Skeletal manipulation method

ABSTRACT

A method of treating scoliosis in a subject includes securing a scoliosis treatment device to first and second locations on the subject&#39;s skeletal system, the scoliosis treatment device including a first portion, a second portion moveably mounted relative to the first portion, and an adjustment device disposed on the device and configured to change a distraction force between the first location and the second location, the adjustment device including a rotationally mounted magnetic element configured to move the second portion relative to the first portion in response to rotation of the magnetic element. An external adjustment device is provided external to the subject and is able to adjust the distraction force between the first location and second location.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/433,669 filed on Jun. 6, 2019, which is itself a continuation of U.S.application Ser. No. 15/640,926 filed on Jul. 3, 2017, now issued asU.S. Pat. No. 10,349,995, which itself is a continuation of U.S.application Ser. No. 14/880,980 filed on Oct. 12, 2015, now issued asU.S. Pat. No. 9,693,813, which itself is a continuation of U.S.application Ser. No. 14/629,426 filed on Feb. 23, 2015, now issued asU.S. Pat. No. 9,179,960, which itself is a continuation of U.S.application Ser. No. 13/849,405 filed on Mar. 22, 2013, now issued asU.S. Pat. No. 9,271,781, which itself is a continuation of U.S.application Ser. No. 13/277,980 filed on Oct. 20, 2011, now issued asU.S. Pat. No. 8,419,734, which itself is a continuation of U.S.application Ser. No. 12/121,499, filed May 15, 2008, now issued as U.S.Pat. No. 8,057,472, which itself claims priority to U.S. ProvisionalPatent Application No. 60/983,917 filed on Oct. 30, 2007. Theabove-noted Applications, Patents, and entire contents thereof areincorporated by reference as if set forth fully herein.

FIELD OF THE INVENTION

The field of the invention generally relates to medical devices fortreating disorders of the skeletal system.

BACKGROUND OF THE INVENTION

Scoliosis is a general term for the sideways (lateral) curving of thespine, usually in the thoracic or thoracolumbar region. Scoliosis iscommonly broken up into different treatment groups, AdolescentIdiopathic Scoliosis, Early Onset Scoliosis and Adult Scoliosis.

Adolescent Idiopathic Scoliosis (AIS) typically affects children betweenages 10 and 16, and becomes most severe during growth spurts that occuras the body is developing. One to two percent of children between ages10 and 16 have some amount of scoliosis. Of every 1000 children, two tofive develop curves that are serious enough to require treatment. Thedegree of scoliosis is typically described by the Cobb angle, which isdetermined, usually from x-ray images, by taking the most tiltedvertebrae above and below the apex of the curved portion and measuringthe angle between intersecting lines drawn perpendicular to the top ofthe top vertebrae and the bottom of the bottom. The term idiopathicrefers to the fact that the exact cause of this curvature is unknown.Some have speculated that scoliosis occurs when, during rapid growthphases, the ligamentum flavum of the spine is too tight and hinderssymmetric growth of the spine. For example, as the anterior portion ofthe spine elongates faster than the posterior portion, the thoracicspine begins to straighten, until it curves laterally, often with anaccompanying rotation. In more severe cases, this rotation actuallycreates a noticeable deformity, wherein one shoulder is lower than theother. Currently, many school districts perform external visualassessment of spines, for example in all fifth grade students. For thosestudents in whom an “S” shape or “C” shape is identified, instead of an“I” shape, a recommendation is given to have the spine examined by aphysician, and commonly followed-up with periodic spinal x-rays.

Typically, patients with a Cobb angle of 20° or less are not treated,but are continually followed up, often with subsequent x-rays. Patientswith a Cobb angle of 40° or greater are usually recommended for fusionsurgery. It should be noted that many patients do not receive thisspinal assessment, for numerous reasons. Many school districts do notperform this assessment, and many children do not regularly visit aphysician, so often, the curve progresses rapidly and severely. There isa large population of grown adults with untreated scoliosis, in extremecases with a Cobb angle as high as or greater than 90°. Many of theseadults, though, do not have pain associated with this deformity, andlive relatively normal lives, though oftentimes with restricted mobilityand motion. In AIS, the ratio of females to males for curves under 100is about one to one, however, at angles above 30°, females outnumbermales by as much as eight to one. Fusion surgery can be performed on theAIS patients or on adult scoliosis patients. In a typical posteriorfusion surgery, an incision is made down the length of the back andTitanium or stainless steel straightening rods are placed along thecurved portion. These rods are typically secured to the vertebralbodies, for example with bone screws, or more specifically pediclescrews, in a manner that allows the spine to be straightened. Usually,at the section desired for fusion, the intervertebral disks are removedand bone graft material is placed to create the fusion. If this isautologous material, the bone is harvested from a hip via a separateincision.

Alternatively, the fusion surgery may be performed anteriorly. A lateraland anterior incision is made for access. Usually, one of the lungs isdeflated in order to allow access to the spine from this anteriorapproach. In a less-invasive version of the anterior procedure, insteadof the single long incision, approximately five incisions, each aboutthree to four cm long are made in several of the intercostal spaces(between the ribs) on one side of the patient. In one version of thisminimally invasive surgery, tethers and bone screws are placed and aresecured to the vertebra on the anterior convex portion of the curve.Currently, clinical trials are being performed which use staples inplace of the tether/screw combination. One advantage of this surgery incomparison with the posterior approach is that the scars from theincisions are not as dramatic, though they are still located in avisible area, when a bathing suit, for example, is worn. The stapleshave had some difficulty in the clinical trials. The staples tend topull out of the bone when a critical stress level is reached.

Commonly, after surgery, the patient will wear a brace for a few monthsas the fusing process occurs. Once the patient reaches spinal maturity,it is difficult to remove the rods and associated hardware in asubsequent surgery, because the fusion of the vertebra usuallyincorporates the rods themselves. Standard practice is to leave thisimplant in for life. With either of these two surgical methods, afterfusion, the patient's spine is now straight, but depending on how manyvertebra were fused, there are often limitations in the degree offlexibility, both in bending and twisting. As these fused patientsmature, the fused section can impart large stresses on the adjacentnon-fused vertebra, and often, other problems including pain can occurin these areas, sometimes necessitating further surgery. Many physiciansare now interested in fusionless surgery for scoliosis, which may beable to eliminate some of the drawbacks of fusion.

One group of patients in which the spine is especially dynamic is thesubset known as Early Onset Scoliosis (EOS), which typically occurs inchildren before the age of five, and more often in boys than in girls.This is a more rare condition, occurring in only about one or two out of10,000 children, but can be severe, sometimes affecting the normaldevelopment of organs. Because of the fact that the spines of thesechildren will still grow a large amount after treatment, non-fusiondistraction devices known as growing rods and a device known as theVEPTR—Vertical Expandable Prosthetic Titanium Rib (“Titanium Rib”) havebeen developed. These devices are typically adjusted approximately everysix months, to match the child's growth, until the child is at leasteight years old, sometimes until they are 15 years old. Each adjustmentrequires a surgical incision to access the adjustable portion of thedevice. Because the patients may receive the device at an age as earlyas six months old, this treatment requires a large number of surgeries.Because of the multiple surgeries, these patients have a rather highpreponderance of infection.

Returning to the AIS patients, the treatment methodology for those witha Cobb angle between 20° and 40° is quite controversial. Many physiciansproscribe a brace (for example, the Boston Brace), that the patient mustwear on their body and under their clothes 18 to 23 hours a day untilthey become skeletally mature, for example to age 16. Because thesepatients are all passing through their socially demanding adolescentyears, it is quite a serious prospect to be forced with the choice ofeither wearing a somewhat bulky brace that covers most of the upperbody, having fusion surgery that may leave large scars and also limitmotion, or doing nothing and running the risk of becoming disfigured andpossibly disabled. It is commonly known that many patients have at timeshidden their braces, for example, in a bush outside of school, in orderto escape any related embarrassment. The patient compliance with bracewearing has been so problematic, that there have been special bracesconstructed which sense the body of the patient, and keep track of theamount of time per day that the brace is worn. Patients have even beenknown to place objects into unworn braces of this type in order to foolthe sensor. Coupled with the inconsistent patient compliance with braceusage, is a feeling by many physicians that braces, even if usedproperly, are not at all effective at curing scoliosis. These physiciansmay agree that bracing can possibly slow down or even temporarily stopcurve (Cobb angle) progression, but they have noted that as soon as thetreatment period ends and the brace is no longer worn, often thescoliosis rapidly progresses, to a Cobb angle even more severe than itwas at the beginning of treatment. Some say the reason for the supposedineffectiveness of the brace is that it works only on a portion of thetorso, and not on the entire spine. Currently a prospective, randomized500 patient clinical trial known as BrAIST (Bracing in AdolescentIdiopathic Scoliosis Trial) is enrolling patients, 50% of whom will betreated with the brace and 50% of who will simply be watched. The Cobbangle data will be measured continually up until skeletal maturity, oruntil a Cobb angle of 50° is reached, at which time the patient willlikely undergo surgery.

Many physicians feel that the BrAIST trial will show that braces arecompletely ineffective. If this is the case, the quandary about what todo with AIS patients who have a Cobb angle of between 20° and 40° willonly become more pronounced. It should be noted that the “20° to 40°”patient population is as much as ten times larger than the “40° andgreater” patient population.

Currently, genetic scientists are at work to find one or more genes thatmay predispose scoliosis. Once identified, some are still skeptical asto whether gene therapy would be possible to prevent scoliosis, howeverthe existence of a scoliosis gene would no doubt allow for easier andearlier identification of probable surgical patients.

SUMMARY OF THE INVENTION

In a first embodiment, a method of treating scoliosis in a subjectincludes securing a scoliosis treatment device to first and secondlocations on the subject's skeletal system, the scoliosis treatmentdevice including a first portion, a second portion moveably mountedrelative to the first portion, and an adjustment device disposed on thedevice and configured to change a distraction force between the firstlocation and the second location, the adjustment device including arotationally mounted magnetic element configured to move the secondportion relative to the first portion in response to rotation of themagnetic element. An external adjustment device is provided external tothe subject, the external adjustment device including a first rotatingmagnet adapted to rotate about a first axis and a second rotating magnetspaced apart from the first rotating magnet and adapted to rotate abouta second, separate axis. The implant is adjusted non-invasively bymoving the first and second rotating magnets of the external adjustmentdevice so as to increase the distraction force between the firstlocation and second location.

In another embodiment, a method of treating scoliosis includes securinga scoliosis treatment device to first and second locations on thesubject's skeletal system, the scoliosis treatment device including afirst portion, a second portion moveably mounted relative to the firstportion, and an adjustment device disposed on the device and configuredto change a distraction force between the first location and the secondlocation, the adjustment device having a rotationally mounted magneticelement. An external adjustment device is provided external to thesubject, the external adjustment device including first and secondrotating magnetic fields rotating about separate axes, the first andsecond rotating magnetic fields being disposed on the same side of thesubject's body. The implant is non-invasively adjusted by rotating thefirst and second magnetic fields of the external adjustment device so asto increase the distraction force between the first location and secondlocation.

In still another embodiment, a method of treating scoliosis in a subjectincludes identifying a genetic susceptibility of a subject having a Cobbangle of less than or equal to 30° to develop a Cobb angle of greaterthan or equal to 40°. A scoliosis treatment device is secured to firstand second locations on the subject's skeletal system, the scoliosistreatment device including a first portion, a second portion moveablymounted relative to the first portion, and an adjustment device disposedon the device and configured to change a distraction force between thefirst location and the second location, the adjustment device having arotationally mounted magnetic element. An external adjustment device isprovided external to the subject, the external adjustment device havingat least one rotating magnet adapted to rotate about an axis. Theimplant is non-invasively adjusted by rotating the at least one rotatingmagnet of the external adjustment device.

In still another embodiment, a method of non-invasively adjusting amagnetically-driven device implanted within a subject includes locatingthe subject within a magnetic field created by a magnetic resonantimaging instrument and rotating the subject about an axis of rotation.

In yet another embodiment, a method of treating scoliosis in askeletally mature subject having an initial Cobb angle of more than 40°includes securing a scoliosis treatment device to first and secondlocations on the subject's skeletal system, the scoliosis treatmentdevice including a first portion, a second portion moveably mountedrelative to the first portion, and an adjustment device disposed on thedevice and configured to change a distraction force between the firstlocation and the second location, the adjustment device having arotationally mounted magnetic element. An external adjustment device isprovided external to the subject, the external adjustment deviceincluding at least one rotating magnet adapted to rotate about an axis.The implant is periodically adjusted in a non-invasive manner byrotating the at least one rotating magnet of the external adjustmentdevice so as to reduce the Cobb angle of the subject from the initialCobb angle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the spine of a person with scoliosis.

FIG. 2 illustrates the Cobb angle of a scoliotic spine.

FIG. 3 illustrates the large incision made during prior art scoliosisfusion surgery.

FIG. 4 illustrates a two rod embodiment of the present invention.

FIG. 5 illustrates a posterior view of the two rod embodiment of thepresent invention.

FIG. 6A illustrates a sectional view of a single rod in accordance withan embodiment of the present invention taken through line 6A-6A of FIG.5.

FIG. 6B illustrates a detailed view of portion A of FIG. 6A inaccordance with an embodiment of the present invention.

FIG. 6C illustrates a detailed view of portion B of FIG. 6A inaccordance with an embodiment of the present invention.

FIG. 6D illustrates a detailed view of portion C of FIG. 6C inaccordance with an embodiment of the present invention.

FIG. 6E illustrates an end view of a cylindrical magnetic member foractuating a clamp in accordance with an embodiment of the presentinvention.

FIG. 6F illustrates an end view of a cylindrical magnetic member foradjusting a distraction device in accordance with an embodiment of thepresent invention.

FIG. 6G illustrates the internal planetary gearing of portion of FIG. 7Cin accordance with an embodiment of the present invention.

FIG. 7 illustrates the two smaller incisions which are possible usingthe system of the invention.

FIG. 8 illustrates a single small incision which is possible usinganother embodiment of the system of the invention.

FIG. 9 illustrates a patient with an implanted distraction device duringa non-invasive adjustment procedure.

FIG. 10 illustrates a perspective view of an external adjustment deviceaccording to one embodiment. The outer housing or cover is removed toillustrate the various aspects of the external adjustment device.

FIG. 11 illustrates a side or end view of the external adjustment deviceof FIG. 10.

FIG. 12 illustrates a perspective view of an external adjustment deviceof FIG. 10 with the outer housing or cover in place.

FIG. 13A illustrates a cross-sectional representation of the externaladjustment device being positioned on a patient's skin. FIG. 13Aillustrates the permanent magnet of the implantable interface in the 0°position.

FIG. 13B illustrates a cross-sectional representation of the externaladjustment device being positioned on a patient's skin. FIG. 13Billustrates the permanent magnet of the implantable interface in the 90°position.

FIG. 13C illustrates a cross-sectional representation of the externaladjustment device being positioned on a patient's skin. FIG. 13Cillustrates the permanent magnet of the implantable interface in the180° position.

FIG. 13D illustrates a cross-sectional representation of the externaladjustment device being positioned on a patient's skin. FIG. 13Dillustrates the permanent magnet of the implantable interface in the270° position.

FIG. 14 schematically illustrates a system for driving the externaladjustment device according to one embodiment.

FIGS. 15-22 illustrate cross-sectional views of the driven magnet alongwith the acoustic or sonic indicator housing illustrating the rotationalorientation of the magnet and the magnetic ball. Various states areillustrated as the magnet rotates in the clockwise direction.

FIGS. 23-30 illustrate cross-sectional views of the driven magnet alongwith the acoustic or sonic indicator housing illustrating the rotationalorientation of the magnet and the magnetic ball. Various states areillustrated as the magnet rotates in the counter-clockwise direction.

FIG. 31 illustrates the acoustic signal as a function of time of anembodiment of the invention having an acoustic or sonic housing thatcontains a magnetic ball. Peaks are seen every 2 rotation of the drivenmagnet in the counter-clockwise direction.

FIG. 32 illustrates the acoustic signal as a function of time of anembodiment of the invention having an acoustic or sonic housing thatcontains a magnetic ball. Peaks are seen every % rotation of the drivenmagnet in the clockwise direction.

FIG. 33 illustrates the frequency response of the acoustic or sonichousing of the type illustrated in FIGS. 15-30 during counter-clockwiserotation of the driven magnet.

FIG. 34 illustrates the frequency response of the acoustic or sonichousing of the type illustrated in FIGS. 15-30 during clockwise rotationof the driven magnet.

FIG. 35 illustrates a system for driving an internally located drivenmagnet via an external device using a feedback mechanism.

FIG. 36 illustrates a distraction device affixed to a spine of a patientaccording to one embodiment.

FIG. 37 illustrates a distraction device according to anotherembodiment. Anchors in the form of hooks are illustrated at opposingends of the distraction rod.

FIG. 38 illustrates a side view of a pedicle screw system used inaccordance with the embodiment illustrated in FIG. 36.

FIG. 39 illustrates the connection between an adjustable portion of thedistraction device and a connecting rod that allows for, among othermovements, free rotation.

FIG. 40 is a perspective view of an adjustable portion of a distractiondevice according to another embodiment.

FIG. 41 is a perspective view of a remotely located magnetic adjustmentdevice that is used in connection with the adjustable portionillustrated in FIG. 40.

FIG. 42 illustrates a perspective view of a cylindrical magnet that ismagnetized in the radial direction according to one embodiment.

FIG. 43 illustrates a perspective view of a distraction device accordingto another embodiment.

FIG. 44 illustrates the adjustable portion of FIG. 43 without the cover.

FIG. 45 illustrates a clamp used to affix the distraction device to apatient's anatomical structure according to one embodiment.

FIG. 46 illustrates a clamp used to affix the distraction device to apatient's anatomical structure according to another embodiment.

FIG. 47 illustrates an adjustable portion of a distraction deviceaccording to one embodiment.

FIG. 48 illustrates a cross-sectional view of the adjustable portion ofFIG. 47 taken along the line 48-48 of FIG. 47.

FIG. 49 illustrates an adjustable portion of a distraction deviceaccording to one embodiment.

FIG. 50 illustrates a cross-sectional view of the adjustable portion ofFIG. 49 taken along the line 50-50 of FIG. 49.

FIG. 51 illustrates an embodiment of a distraction device that includestwo (2) adjustable rods, which each rod being independently adjustable.

FIG. 52 illustrates a technique of performing an emergency adjustment ofa magnetically-actuated distraction device.

FIG. 53 illustrates an embodiment of a distraction device disposed on abone.

FIG. 54 illustrates an embodiment of a distraction device disposedwithin the intramedullary canal of a bone.

FIG. 55 illustrates an embodiment of a distraction device forintervertebral placement.

FIG. 56 illustrates a fractured vertebral body.

FIG. 57 illustrates a distraction device being placed into the vertebralbody of FIG. 56.

FIG. 58 illustrates a distraction device within a vertebral body.

FIG. 59 illustrates a distraction device manipulated to add height to avertebral body.

FIG. 60 illustrates an alternative configuration of a distraction devicefor use in a vertebral body.

FIG. 61 illustrates a non-invasively adjustable dynamic stabilizationdevice.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1 illustrates a patient 100 with scoliosis. The concave portion 102of the spinal curve can be seen on the left side 104 of the patient 100,and the convex portion 106 can be seen on the right side 108 of thepatient 100. Of course, in other patients, the concave portion 102 mayappear on the right side 108 of the patient 100 while the convex portion106 may be found on the left side 104 of the patient. In addition, asseen in FIG. 1, some rotation of the spine 110 is present, andunevenness between the left shoulder 112 and right shoulder 114 is seen.

FIG. 2 illustrates the Cobb angle 116 of a spine 110 of a patient withscoliosis. To determine the Cobb angle, lines 118 and 120 are drawn fromvertebra 122 and 124, respectively. Intersecting perpendicular lines 126and 128 are drawn by creating 90° angles 130 and 132 from lines 118 and120. The angle 116 created from the crossing of the perpendicular lines126 and 128 is defined as the Cobb angle. In a perfectly straight spine,this angle is 0°.

In many Adolescent Idiopathic Scoliosis (AIS) patients with a Cobb angleof 40° or greater, spinal fusion surgery is typically the first option.FIG. 3 illustrates a long incision 134 formed in the patient 100 whichis typically made during posterior scoliosis fusion surgery. This typeof fusion surgery is known in the prior art. The long incision 134extends between an upper end 136 and a lower end 138. The length of thisincision 134 is longer than the length of the section of the vertebra tobe fused. The actual length between the upper end 136 and the lower end138 varies, depending on the size of the patient, and the extent of thescoliosis, but in AIS patients this length is significantly longer than15 cm. More typically, it is longer than 25 cm.

FIGS. 4 and 5 illustrate a distraction device 140 for treating scoliosisaccording to one embodiment of the invention. The distraction device140, which is an implantable device, includes a first adjustable rod 142and a second adjustable rod 144. For patient distraction, a firstadjustable rod 142 is positioned on one side of the spine 110 while thesecond adjustable rod 144 is positioned on the opposing side of thespine 110. The spine 110 is omitted from view in FIGS. 4 and 5 for sakeof clarity. While the distraction device 140 illustrated in FIGS. 4 and5 comprises first and second adjustable rods 142, 144, it should beunderstood that in alternative embodiments, the distraction device 140may include just a single adjustable rod 142 (the second adjustable rod144 being omitted entirely) that is implanted within the patient.

Referring back to FIGS. 4 and 5, each adjustable rod 142, 144 includes afirst elongate member 146, 148 and a second elongate member 150, 152,that are coupled together by an adjustable portion 158, 159. Theadjustable portions 158, 159 include a variable overlapping regionbetween the first elongate members 146, 148 and the second elongatemembers 150, 152 which allows for the non-invasive adjustment of thelength of each adjustable rod 142, 144. In this particular embodiment,the first elongate elements 146, 148 are telescopically contained withinhollow receiving portions of the second elongate elements 150, 152, andthe adjustable portions 158, 159 are substantially straight. Asillustrated, the adjustable rods 142, 144 have an upper curve 154 and alower curve 156, which allow them to better conform to the naturalfront-to-back curve of the spine. For example, the upper curve 154conforms to the normal kyphosis of the upper thoracic region and thelower curve 156 conforms to the normal lordosis of the lumbar region. Inone aspect of the invention, the curved portions 154, 156 are bendablein order to better conform with a patient's specific spinalconfiguration. For the example, the curved portions 154, 156 may be madeof a malleable or elastic-type material such that the surgeon canmanually alter the particular shape of each adjustable rod 142, 144 tothe specific needs of the patient. In a large number of scoliosispatients, especially adolescent idiopathic scoliosis patients, thescoliotic curve does not include the lower lumbar levels of the spineand so the lower curve 156 is not necessary. As explained above, theembodiment illustrated in FIGS. 4 and 5 represents a dual rodconfiguration. With this configuration, both rods 142, 144 are insertedthrough the same incision, and can be placed along the spine 110 on twoopposite sides of the center line of the spine 110. Alternatively, eachmay be placed through its own, smaller incision.

Alternatively, a single adjustable rod version 142 can be used,preferably positioned on the concave side of the scoliosis curve. Yetanother variation includes a single adjustable rod 142 that does nothave either or both of the curves (i.e., curves 154 and 156 omitted). Astraight adjustable rod 142 of this nature may be placed further lateral(to the side of the spine 110), and not necessarily have to hug thefront-to-back contours of the spine 110 or the muscle covering the spine110. In still another embodiment, the first elongate member (e.g., 146,148) and the second elongate member (e.g., 150, 152) do not telescope inrelation to one another, but rather are in parallel, at least along theadjustable portion 158, 159. The distraction device 140 is implanted inthe patient 100 in order to straighten the scoliotic spine 110. For thisreason, each end of the adjustable rods 142, 144 advantageously containsan anchor 161 that allows for securement to a location in the skeletalsystem. For example, the anchor 161 at either end may include a clampfor clamping to a skeletal structure. Alternatively, either end maycomprise a bracket for securing to a section of bone with the use of abone screw or pedicle screw. The embodiment in FIG. 4 illustrates aclamp 160, 162 at the upper end of the first elongate members 146, 148and brackets 164 at the end of the second elongate members 150, 152. Thebrackets 164 can be secured to the second elongate members 150, 152 by avariety of methods, including set screws, welding, soldering, swaging,crimping or mechanical joints. Screws 166 secure the brackets 164 tobony structures, such as the vertebral bodies or the sacrum. The clamp160, 162 can be used to clamp the distraction device 140 to a rib or thearticulation of the rib with the vertebra at the facet. FIGS. 37 and 38,which are described in more detail below, illustrate alternative anchors161 that may be used to secure the first elongate members 146, 148 orsecond elongate members 150, 152 to the skeletal structure.

The distraction device 140 is configured such that the adjustableportion(s) 158, 159 change at least one of the distance or force betweenthe anchor or affixation points (e.g., at the spine or other anatomicalstructure) of the first elongate member(s) 146, 148 and the secondelongate member(s) 150, 152. For example, the adjustable portion(s) 158,159 may increase the length between the anchor or affixation points.Similarly, the adjustable portion(s) 158, 159 may increase the force(e.g., distraction force) between the anchor or affixation points. Theadjustable portion(s) 158, 159 may alter both the distance and force atthe same time.

FIG. 6A illustrates a sectional view of the first adjustable rod 142indicating the location of the adjustable portion 158 and the clamp 160.The tip 168 of clamp 160 is shaped to allow for blunt dissection oftissue, so that the adjustable rod 142 may be placed under the skin andpushed for much of the length of the spine 110, so that a large portionof the long incision 134 of FIG. 3 is not necessary. This allows for,for instance, alternative incision geometry, such as that illustrated inFIG. 7. As seen in FIG. 7, a lower incision 170 is made having an upperend 176 and a lower end 178 (for example, by a scalpel) and the firstadjustable rod 142 is placed through the lower incision 170 and underthe skin. Using a dissection technique, the first adjustable rod 142 isinserted under the skin along an intermediate area 174. The dissectiontechnique may include the use of a scope (laparoscope, arthroscope,endoscope, or the like) and an additional dissecting tool, but usuallycan be done without these tools. The additional dissecting tool mayinclude, for example, a tapered sheath, which is advanced over the firstadjustable rod 142, dissecting the tissue along the way, while beingvisualized by scope, for example on a monitor. Alternatively, theadditional dissecting tool may be a blunt dissecting tool, consisting oftwo fingers which can be spread apart and brought together, once again,while being visualized by the scope.

Once the clamp 160 of the first adjustable rod 142 (as seen in FIG. 6A)is advanced to the location near the anatomy to be clamped, an upperincision 172 is made having an upper end 180 and a lower end 182 and thelocation near the anatomy to be clamped is exposed by dissection. Theclamp 160 is then actuated to clamp this anatomical structure, andadditionally, the opposite end of the first adjustable rod 142 issecured, for example by a bone screw (e.g., pedicle screw) and bracketcombination. The adjustment device of the adjustable rod 142 (to bedescribed later) may be adjusted prior to the securement of either endof the first adjustable rod 142, so that the desired length is achieved.After securement of both ends, first adjustable rod 142 may then beadjusted in order to adjust the distraction distance or distractionforce between the two locations in the anatomy to a desired amount. Inone aspect of the invention, the length of the first adjustable rod 142may first be adjusted manually by the physician without using theremotely-operated adjustment device as described herein. For example,the initial length of the adjustable rod 142 may be manually set by thephysician by pushing or pulling the first and second elongate members146, 150 relative to one another. Alternatively, the length of theadjustable rod 142 may be adjusted by trimming or removing a portion ofthe length of the adjustable rod 142.

By having the physician adjust the length of the adjustable rod 142during initial placement, a distraction force may be applied to thespine 110 without having to use any displacement distance or force thatis provided by the remotely-operated adjustment device. For example,there typically is a limited degree of movement that is provided by theremotely-operated adjustment device. When the physician applies a firstor initial distraction force upon implantation, the budget of availabledisplacement for the remotely-operated adjustment device is saved forlater adjustments.

Still referring to FIG. 7, the two incisions are then closed usingstandard techniques. As described, the single long incision is nowreplaced by two, shorter incisions 170, 172, whose combined length whenadded together is less than the length of the single long incisionillustrated in FIG. 3. For example, lower incision 170 and upperincision 172 each has a length of less than 15 cm, and preferably, eachhas a length of less than 7.5 cm, and more preferably, less than 5 cm.

An optional magnetic clamping device is illustrated in FIG. 6B, whichallows for the entire procedure to be done under a single short incision184, as seen in FIG. 8. As previously described, a single short incision184 having an upper end 186 and a lower end 188 is made (for example, bya scalpel) and the first adjustable rod 142 is placed through the singlesmall incision 184 and under the skin. Using a dissection technique, thefirst adjustable rod 142 is inserted under the skin towards the uppertarget location. As previously described, this dissection technique mayinclude the use of a scope (laparoscope, arthroscope, endoscope, or thelike) and an additional dissecting tool. Once the clamp 160 of the firstadjustable rod 142 is advanced to the location near the anatomy to beclamped, one or more dissecting tools and a scope are used to expose thetarget location, for example a rib or facet articulation. Referring toFIG. 6B, the magnetically-operated clamp 160 includes a first finger 190and a second finger 192. The first finger 190 is permanently coupled tofirst elongate element 146 while the second finger 192 is longitudinallyadjustable in relation to first finger 190, so that gap 194 may beincreased or decreased in response to actuation. A closure device 198 isoperated by an external adjustment device such as that illustrated inFIGS. 10-12 in order to increase or decrease gap 194, and therefore openor close clamp 160. As will be described, the clamp 160 is magneticallyadjustable, and so the clamping process may be performed non-invasively,therefore making a second incision unnecessary.

The magnetically-operated clamp 160 may be particularly useful if, asexpected, the evidence of the ineffectiveness of braces becomesstronger, many physicians will be searching for less invasive proceduresto treat scoliosis. Patients will demand that the procedures be asminimally invasive as possible, and one of the big elements in theirdecision to undergo surgery is the size of the incision, and thus sizeof the scar, both during and after healing. AIS patient whose Cobbangles are greater than 40° are more likely to be treated with fusionsurgery, but patients in the 20° to 40° range may be treatable usingfusionless methods which harness the growing power of their spine.Currently, it is known that female AIS patients who have not yet reachedmenarche (the first menstrual period) are more likely to have a curvethat will progress further. Additionally, AIS patients whose age isyounger are more likely to have their curves progress. One or more“scoliosis genes” have recently been discovered, and work is being doneto create a genetic test that allows identification of a patient whosecurve is very likely to progress beyond 40° at a time when her Cobbangle is less than 40°, for example 20°. Because braces are aquestionable option, it is expected that a minimally invasive,non-fusion procedure will be the procedure of choice for these patients.Though the incision 184 in FIG. 8 is depicted as a vertical incision,alternatively, it may be made horizontally. For example, the horizontalincision may be made so that it is just below and parallel to the“bikini line”, allowing the resulting scar to be more concealed. Thiscould also be done with incision 170 in FIG. 7.

Returning to FIG. 6B, closure device 198 includes a cylindrical magneticmember 200, which can be activated by magnetic coupling with an externaladjustment device (such as external adjustment device 1130 illustratedin FIGS. 10-12). Though configurations may vary for this closure device198, in this particular embodiment, magnetic member 200 is a hollow rareearth magnet, preferably Neodymium-Iron-Boron. As seen from an end viewin FIG. 6E, the magnetic member 200 has a threaded insert 202 having afemale thread so that when the magnetic member 200 rotates, the threadedinsert 202 rotates in unison. Magnetic member 200 is a permanent magnet217 having a north pole 204 and a south pole 206. Magnetic member 200 ispreferably coated with a material, for example Parylene, phenolic resinor Gold, which is non-magnetic, but protective and biocompatible in abody implant application. In certain embodiments, the individual Nd—Fe—Bmagnets are enclosed within a stainless steel casing/housing or variouslayers of nickel, gold or copper plating to protect the corrosiveNd—Fe—B material from the environment inside the body. In otherembodiments, other magnetic materials may be used, including SmCo(Samarium Cobalt), which is typically available as SmCo₅, or SmCo₁₅,Sm₂Co₁₇, or AlNiCo (Aluminum Nickel Cobalt). In still other embodiments.Iron Platinum (Fe—Pt) may be used. Iron platinum magnets achieve a highlevel of magnetism without the risk of corrosion, and may possiblypreclude the need to encapsulate. In yet other embodiments, thepermanent magnets 217 on the implantable interface may be replaced bymagnetically responsive materials such as Vanadium Permendur (also knownas Hiperco).

It should be noted that magnetic member 200 can also be hermeticallysealed within the first elongate element 146. When the externaladjustment device 1130 is operated, it applies a moving magnetic field,which causes magnetic member 200 to rotate. Attached to the secondfinger 192 is a threaded rod 210 which threadedly engages the femalethread of the threaded insert 202. When the magnetic member 200 isrotated by the external adjustment device 1130 in a first direction, thethreaded rod 210 moves in a first longitudinal direction 212, causingthe second finger 192 to move away from the first finger 190, and thegap 194 to open. There may also be a manual adjustment mechanism on theclamp 160 so that the clamp 160 may be opened outside the patient, inpreparation for the procedure. When gap 194 is adjusted to be wider thanthe anatomical structure, for example rib, around which the clamp 160 isto be secured, then through visualization by the scope and manipulationwith the dissecting tools, the clamp 160 is placed over the rib, so thatrib is contained in cavity 196. At this point the external adjustmentdevice 1130 is operated so that it turns the magnetic member 200 in theopposite direction causing the threaded rod 210 to move longitudinallyin a second direction 214, and the two fingers 190, 192 close around therib. The gap 194 is now smaller than the width of the rib, and thus, theclamp 160 is secure. If the implant is to be removed at a later date,the magnetic clamp mechanism may also be used to remove the implantwithout having to make an incision adjacent the clamp.

FIG. 6C illustrates a sectional view of the adjustable portion 158 ofthe first adjustable rod 142. FIG. 6D illustrates a detail of theadjustment device 232. The first elongate element 146 is telescopicallycontained within the second elongate element 150. The cross-sectionalshapes of the first elongate element 146 and the second elongate element150 may be circular or non-circular, so that they cannot rotate withrespect to each other (for example, a keyed configuration). One or bothof the elongate elements 146, 150 may contain ribs along the crosssection of the adjustable portion 158 in order to minimize contactsurface area between the first elongate element 146 and the secondelongate element 150 and thus lower frictional resistance. Beveled endpiece 216 attached to the second elongate element 150 may serve twopurposes. First, it allows for smooth insertion and no catching intissue when the first adjustable rod 142 is inserted under the skin.Second, it serves as a low friction dynamic seal over the first elongateelement 146. Magnetic element 218 comprises a cylindrical permanentmagnet which is poled as shown in FIG. 6F. Alternatively, magneticelement 218, may be made from any of the materials described formagnetic member 200 in FIG. 6B. Magnetic element 218 is rotatablysecured to an inner cavity 234 of second elongate element 150 by ahousing, in this case an acoustic housing 222. A ball bearing 220 isillustrated at one end of the magnetic element 218 in order to reducerotational friction. A second ball optional bearing (not shown) can beincluded on the opposite end of the magnetic element 218. Magneticelement 218 is rotated by an external adjustment device 1130 whichproduces a moving magnetic field.

As seen in FIG. 6D, the magnetic element 218 is coupled to a planetarygear set 224, for example, having a 4:1, 16:1 or 64:1 gear reduction, orgreater. The purpose of the gear reduction is two-fold. First, it allowsthe distraction device 140 to be adjusted with a smaller input torquerequirement. Second, it adds precision to the adjustment, because alarger number of turns of the magnetic element 218 are required for eachadjustment interval. Planetary gear set 224 is shown in detail in FIG.6G. Sun gear 236 is turned in a one-to-one fashion by the rotation ofthe magnetic element 218. Sun gear 236 engages a plurality of planetarygears 238 (in this case, four are pictured). Planetary gears 238 engageand turn ring gear 240 which is attached to a lead screw 226 via acoupling 228. The gear ratio is the number of teeth in the ring gear 240divided by the number of teeth in the sun gear 236. For example if thering gear 240 has four times as many teeth as the sun gear 236, then thegear ratio is 4:1. In this case, only 25% of the torque is required todrive the lead screw 226 as would have been required to drive itdirectly, ignoring the variance due to frictional factors. As lead screw226 turns, it threadedly engages with female thread 230, disposed withinend 242 of first elongate element 146. The pitch of lead screw 226threads is preferably very fine pitch, for example, 40 to 120, or morespecifically 80 to 100 threads per inch, in order to minimize frictionbetween the lead screw 226 and the female thread 230, and thus, minimizethe required torque. The materials of the lead screw 226, the rods andother components may be made from non-magnetic, implantable materialssuch as Titanium or Titanium alloys such as Titanium-6% Al-4% V,although they may also be made from other magnetic materials such asstainless steel.

When the magnetic element 218 is rotated by the external adjustmentdevice 1130, the drive train or drive element that is operativelycoupled to the rotatable magnetic element 218 drives the lead screw 226which changes the length of the adjustable portion 158 of the adjustablerod(s) 142, 144. Rotation of the magnetic element 218 in a firstdirection increases the distance between the anchors 161 located onopposing ends of the adjustable rod(s) 142, 144. Conversely, rotation ofthe magnetic element 218 in a second (opposing) direction decreases thedistance between the anchors 161 located on opposing ends of theadjustable rod(s) 142, 144.

Currently, devices such as the VEPTR, which can be surgically adjusted,are used for early onset scoliosis patients, and their adjustability isused for the purpose of keeping up with the dimensional growth of thepatient. It is a purpose of the present invention to create a devicewhich can be non-invasively adjusted in early onset scoliosis patients,but additionally, in adolescent idiopathic scoliosis (AIS) patients andeven adult scoliosis patients. The main purpose for the adjustment inAIS patients is to maintain a distraction force, which in a fusionlessgrowing spine serves to steer growth in the desired manner. Currently,in fusionless surgery, non-adjustable distraction devices are actuatedat very high distraction forces, because the physicians know that overtime, growth and/or changes within the tissue, will cause thisdistraction force to lessen, possibly becoming less effective with time.Because of these high distraction forces, it is not uncommon to haverods break inside the patient, or for bone screws to become dislodged,due to the high stresses. It has been contemplated that the high forcesthat have been measured in some distraction devices of well over 100pounds, are not necessary at any given time to provide correct growthguidance, and that a distraction force of below 45 pounds, and even aslow as 20 pounds may be effective in maintaining the desired growth ofthe spine, especially the unfused spine. That is, as long as this forcecan be maintained, which is not currently possible in prior art deviceswithout surgical intervention. The present invention allows this lowerforce to be continually maintained through non-invasive adjustment. Thebenefit is that lower stresses can be maintained on the bone screws,clamps, and other attachment means as well as the rods themselves,making for a more reliable and durable system. In addition, through theidentification of an optimum distraction force, this desired force canbe maintained throughout the treatment of the patient post-surgery, byfrequent non-invasive adjustments, which can be performed in a doctor'sor nurses office, by a physician or non-physician medical personnel, oreven by the patient herself at home. In addition, by incorporating anoptional force transducer, as part of the distraction device, that isread telemetrically, each adjustment can be done to the precise desireddistraction force. Additionally, a slip clutch 244, is in line with themagnetic element 218 can be pre-adjusted by the physician, or during themanufacturing process, so that during each adjustment, the adjustmentstops when a critical torque (corresponding to the maximum desireddistraction force) is reached. For example, the maximum desireddistraction force may be set at 45 pounds. The slip clutch 244 isillustrated in FIG. 6D as being located between the magnetic element 218and the planetary gear set 224, but it is within the scope of theinvention that the slip clutch 244 may be located at any other stepalong the torque transmission chain.

FIG. 9 illustrates a patient 100 with a distraction device 140 implantedon the left side of the spine 110. Though the spine 110 is visible inFIG. 9 for reference, FIG. 9 is actually meant to depict a non-invasiveadjustment procedure, and so the patient 100 would typically have allincisions healed and could be wearing clothes. The clamp 160 of thedistraction device 140 is secured to a rib 246 at its articulation witha thoracic vertebra 247. A bracket 164 is secured, in this case to alumbar vertebra with screws 166. Alternatively, the bracket 164 may besecured, for example, to the sacrum 249. A radio frequencyidentification (RFID) chip 250 is optionally disposed on the secondelongate element 150 of the distraction device 140 in accordance with anembodiment of the present invention. An RFID (radio frequencyidentification) chip 250 may be implanted in a patient during theimplantation of the distraction device 140. In certain embodiments, theRFID chip 250 may be implanted subcutaneously in a known location, suchas a location near the distraction device 140. In other embodiments, theRFID chip 250 may be located on or within the distraction device 140. Anexternal adjustment device 248 is depicted after being placed againstthe back of the patient 100. Upon the implantation of the distractiondevice 140 or after surgical recovery, the external adjustment device248 stores patient information on the RFID chip 250, including thecurrent size or setting of the distraction device 140, the amountadjusted, the serial number of the distraction device 140, the date ofthe implantation procedure, patient name, distraction force, adjustmenttorque, and identification. During subsequent adjustment procedures, theexternal adjustment device 248 may read the RFID chip 250 to determineinformation related to the patient, such as the current size or settingof the distraction device 140. At the end of the adjustment procedure,the external adjustment device 248 may store updated patientinformation, including the size or setting of the distraction device140, to the RFID chip 250. An RFID antenna 252 in the externaladjustment device 248 may be used to power the RFID chip in orderfacilitate the read and write functions.

Several techniques may be used to determine the adjustment setting(current size, distraction force or condition) of the distraction device140. For example, the adjustment setting may be determined indirectly bythe number of rotations of one of the rotating components of theexternal adjustment device 248. In certain embodiments, the adjustmentsetting may be determined by the number of rotations of some dynamiccomponent of the adjustable portion 158 of the distraction device 140,by the number of rotations of any one of the gears or shafts of thedistraction device 140, or by the number of rotations of the magneticelement 218. In other embodiments, a feedback mechanism, such as a Halleffect device (two additional magnets that move axially in relation toeach other as the lead screw 226 rotates and therefore as thedistraction device changes its condition), may be used to determine thecurrent adjustment setting of the distraction device 140. A strain gaugeor force transducer disposed on a portion of the distraction device 140may also be used as an implantable feedback device. For example, thestrain gauge may be able to communicate wirelessly the actualdistraction force applied to the spine by the distraction device 140. Awireless reader or the like (that also can inductively power the straingauge) may be used to read the distraction forces. One exemplary straingauge sensor is the EMBEDSENSE wireless sensor, available fromMicroStrain, Inc. of Williston, Vt. 05495. The EMBEDSENSE wirelesssensor uses an inductive link to receive power form an external coil andreturns digital stain measurements wirelessly.

In still other embodiments, an optical encoder feedback mechanism may beused by placing an optical encoder in line with one of the rotatingcomponents of the adjustable portion 158 of the distraction device 140.A through-the-skin optical encoder is even envisioned that shines alight through the skin and fat and counts successive passes of one ormore reflective stripes on the specific rotatable component. In otherembodiments, the external adjustment device 248 may include an audiosensor to determine the current adjustment setting of the distractiondevice 140. For example, the sensor may listen to the cycling sound ofgearing, thus giving feedback information on the amount of totaladjustment. An additional acoustic feedback device is discussed below.

It should be understood that any of the materials of the distractiondevice 140 can be made from radiopaque materials, so that the position,condition or alignment of the components may be seen during the initialsurgical procedure, or during the subsequent adjustment procedures, byuse of X-ray. For example, a circumferential notch or alternatively acircumferential bump disposed on the first or second elongate members148, 146 may be used so that the distance between this notch or bump andsome portion of the second elongate members 150, 152 can be measuredeasily via an X-ray.

It is conceived that the adjustment procedures would preferably takeplace every three to four weeks in the physicians' clinic. Theadjustment may be done by an orthopedic surgeon, but because of therelative ease of the procedure because of the feedback capabilities ofthe system, the procedure may be done by a nurse practitioner, aphysicians' assistant, a technician, or any other non-M.D. personnel. Itis even conceived that the patient may have an external adjustmentdevice 1130 at home and be able to adjust themselves at an even morefrequent rate. The external adjustment device 1130 can be designed totransmit stored information over the phone to the physician's office.For example, adjustment dates or adjustment parameters such asdistraction force or distraction distance.

FIG. 10 illustrates an external adjustment device 1130 which is oneembodiment of an external adjustment device 248 according to one aspectof the invention. The external adjustment device 1130 may be used toexternally impart rotational motion or “drive” a permanent magnet (e.g.,magnetic element 218) located within the distraction device 140. Theexternal adjustment device 1130 includes a motor 1132 that is used toimpart rotational movement to two permanent magnets 1134, 1136. The twopermanent magnets 1134, 1136 are located in the same driver 1130 and areconfigured for placement on the same side of the body of the patient orsubject. The motor 1132 may include, for example, a DC powered motor orservo that is powered via one or more batteries (not shown) integrallycontained within the external adjustment device 1130. Alternatively, themotor 1132 may be powered via a power cord or the like to an externalpower source. For example, the external power source may include one ormore batteries or even an alternating current source that is convertedto DC.

Still referring to FIG. 10, the two permanent magnets 1134, 1136 arepreferably cylindrically-shaped permanent magnets. The permanent magnetsmay be made from, for example, a rare earth magnet material such asNeodymium-Iron-Boron (NdFeB) although other rare earth magnets are alsopossible. For example, each magnet 1134, 1136 may have a length ofaround 1.5 inches and a diameter of around 1.0 to 3.5 inches. Bothmagnets 1134, 1136 are diametrically magnetized (poles are perpendicularthe long axis of each permanent magnet 1134, 1136). The magnets 1134,1136 may be contained within a non-magnetic cover or housing 1137. Inthis regard, the magnets 1134, 1136 are able to rotate within thestationary housing 1137 that separates the magnets 1134, 1136 from theexternal environment. Preferably, the housing 1137 is rigid andrelatively thin walled at least at the portion directly covering thepermanent magnets 1134, 1136, in order to minimize the gap between thepermanent magnets 1134, 1136 and the internal magnet 1064 (as shown inFIGS. 13A-13D).

As seen in FIG. 10, the permanent magnets 1134, 1136 are rotationallymounted between opposing bases members 1138, 1140. Each magnet 1134,1136 may include axles or spindles 1142, 1144 mounted on opposing axialfaces of each magnet 1134, 1136. The axles 1142, 1144 may be mounted inrespective bearings (not shown) that are mounted in the base members1138, 1140. As seen in FIG. 10, driven pulleys 1150 are mounted on oneset of axles 1142 and 1144. The driven pulleys 1150 may optionallyinclude grooves or teeth 1152 that are used to engage with correspondinggrooves or teeth 1156 (partially illustrated in FIG. 12) containedwithin a drive belt (indicated by path 1154).

Still referring to FIG. 10, the external adjustment device 1130 includesa drive transmission 1160 that includes the two driven pulleys 1150along with a plurality of pulleys 1162A, 1162B, 1162C and rollers 1164A,1164B, 1164C on which the drive belt 1154 is mounted. The pulleys 1162A,1162B, 1162C may optionally include grooves or teeth 1166 used forgripping corresponding grooves or teeth 1156 of the drive belt 1154.Pulleys 1162A, 1162B, 1162C and rollers 1164A, 1164B, 1164C may bemounted on respective bearings (not shown). As seen in FIG. 10, pulley1162B is mechanically coupled to the drive shaft (not shown) of themotor 1132. The pulley 1162B may be mounted directly to the drive shaftor, alternatively, may be coupled through appropriate gearing. Oneroller 1164B is mounted on a biased arm 1170 and thus provides tensionto the belt 1154. The various pulleys 1150, 1162A, 1162B, 1162C androllers 1164A, 1164B, 1164C along with the drive belt 1154 may becontained within a cover or housing 1172 that is mounted to the base1138 (as seen in FIG. 12). For safety and convenience, it may be desiredfor the external adjustment device 1130 to have a removable safety coverthat would be placed over the portion containing the permanent magnets1134, 1136, for example during storage, so that the high magnetic fieldcannot come closely in contact with anything that would be stronglyattracted to it or damaged by it.

As seen in FIGS. 10 and 11, rotational movement of the pulley 1162Bcauses the drive belt 1154 to move around the various pulleys 1150,1162A. 1162B, 1162C and rollers 1164A, 1164B, 1164C. In this regard,rotational movement of the motor 1132 is translated into rotationalmovement of the two permanent magnets 1134, 1136 via the drivetransmission 1160. In one aspect of the invention, the base members1138, 1140 are cut so as to form a recess 1174 that is located betweenthe two magnets 1134, 1136. During use, the external adjustment device1130 is pressed against the skin of a patient, or against the clothingwhich covers the skin (e.g., the external adjustment device 1130 may beused through clothing so the patient may not need to undress). Therecess 1174 allows skin as well as the underlying tissue to gather orcompress within the recessed region 1174 as seen in FIGS. 13A and 13B.This advantageously reduces the overall distance between the externaldrive magnets 1134, 1136 and the magnet 1064 contained within thedistraction device 140. By reducing the distance, this means that theexternally located magnets 1134, 1136 and/or the internal magnet 1064may be made smaller. This is especially useful in the case of an obesepatient.

In one embodiment, the two permanent magnets 1134, 1136 are configuredto rotate at the same angular velocity. In another embodiment, the twopermanent magnets 1134, 1136 each have at least one north pole and atleast one south pole, and the external adjustment device 1130 isconfigured to rotate the first magnet 1134 and the second magnet 1136such that the angular location of the at least one north pole of thefirst magnet 1134 is substantially equal to the angular location of theat least one south pole of the second magnet 1136 through a fullrotation of the first and second magnets 1134, 1136.

FIGS. 13A and 13B illustrate cross-sectional views of the patient havingan implanted distraction device 140 containing an internal magnet 1064.For sake of clarity, the first and second elongate members 146, 150 havebeen removed to illustrate the relationship between the externaladjustment device 1130 and the rotationally-driven internal magnet 1064.The internal magnet 1064 is seen disposed on one side of a vertebra1185. Further, the internal magnet 1064 is seen being outside orexternal with respect to the fascia 1184 and muscle 1186 of the subject.FIGS. 13A and 13B illustrate an obese patient in which skin and othertissue gather within the recess 1174. It should be understood that obeseAdolescent Idiopathic Scoliosis patients are rare, and FIGS. 13A and 13Bgenerally indicate a worst-case situation but as seen in FIGS. 13A and13B the excess skin and other tissue is easily accommodated within therecess 1174 to enable close positioning between the internal magnet 1064and the external drive magnets 1134, 1136. For most AIS patients, theair gap or distance between the internal magnet 1064 and the externaldrive magnets 1134, 1136 is generally one inch or less. In FIGS. 13Athrough 13D, the internal magnet 1064 is depicted somewhat larger thanits size in the preferred embodiment, in order for its poles to be moreclearly visible.

Still referring to FIGS. 10 and 11, the external adjustment device 1130preferably includes an encoder 1175 that is used to accurately andprecisely measure the degree of movement (e.g., rotational) of theexternal magnets 1134, 1136. In one embodiment, an encoder 1175 ismounted on the base member 1138 and includes a light source 1176 and alight receiver 1178. The light source 1176 may include an LED which ispointed or directed toward pulley 1162C. Similarly, the light receiver1178 may be directed toward the pulley 1162C. The pulley 1162C includesa number of reflective markers 1177 regularly spaced about the peripheryof the pulley 1162C. Depending on the rotational orientation of thepulley 1162C, light is either reflected or not reflected back onto thelight receiver 1178. The digital on/off signal generated by the lightreceiver 1178 can then be used to determine the rotational speed anddisplacement of the external magnets 1134, 1136.

FIGS. 13A, 13B. 13C, and 13D illustrate the progression of the externalmagnets 1134, 1136 and the internal magnet 1064 that is located withinthe distraction device 140 during use. Internal magnet 1064 is shown forillustration purposes. Internal magnet 1064 is one possible embodimentof the magnetic element 218 described herein. FIGS. 13A, 13B, 13C, and13D illustrate the external adjustment device 1130 being disposedagainst the external surface of the patient's skin 1180 adjacent thespine (not shown for clarity sake). In the non-invasive adjustmentprocedure depicted, the patient 100 lies in a prone position, and theexternal adjustment device 1130 is placed upon the patient's back.However, the adjustment is conceived possible with the patient insupine, standing or positions. The external adjustment device 1130 isplaced against the skin 1180 in this manner to remotely rotate theinternal magnet 1064. As explained herein, rotation of the internalmagnet 1064 is translated into linear motion via the adjustment device232 to controllably adjust the distraction device 140.

As seen in FIGS. 13A, 13B, 13C, and 13D, the external adjustment device1130 may be pressed down on the patient's skin 1180 with some degree offorce such that skin 1180 and other tissue such as the underlying layerof fat 1182 are pressed or forced into the recess 1174 of the externaladjustment device 1130. FIGS. 13A, 13B, 13C, and 13D show the magneticorientation of the internal magnet 1064 as it undergoes a full rotationin response to movement of the permanent magnets 1134, 1136 of theexternal adjustment device 1130.

With reference to FIG. 13A, the internal magnet 1064 is shown beingoriented with respect to the two permanent magnets 1134, 1136 via anangle θ. This angle θ may depend on a number of factors including, forinstance, the separation distance between the two permanent magnets1134, 1136, the location or depth of where the implantable interface1104 is located, the degree of force at which the external adjustmentdevice 1130 is pushed against the patient's skin. Generally inapplications including some obese patients, the angle θ should be at oraround 90° to achieve maximum drivability (e.g., torque). The inventorshave calculated that in the AIS application, where there are few obesepatients, an angle of about 70° is preferred for the majority ofpatients when the permanent magnets 1134, 1136 have an outer diameter ofabout three (3.0) inches.

FIG. 13A illustrates the initial position of the two permanent magnets1134, 1136 and the internal magnet 1064. This represents the initial orstarting location (e.g., 0° position as indicated). Of course, it shouldbe understood that, during actual use, the particular orientation of thetwo permanent magnets 1134, 1136 and the internal magnet 1064 will varyand not likely will have the starting orientation as illustrated in FIG.13A. In the starting location illustrated in FIG. 13A, the two permanentmagnets 1134, 1136 are oriented with their poles in an N-S/S-Narrangement. The internal magnet 1064 is, however, oriented generallyperpendicular to the poles of the two permanent magnets 1134, 1136.

FIG. 13B illustrates the orientation of the two permanent magnets 1134,1136 and the internal magnet 1064 after the two permanent magnets 1134,1136 have rotated through 90°. The two permanent magnets 1134, 1136rotate in the direction of arrow A (e.g., clockwise) while the internalmagnet 1064 rotates in the opposite direction (e.g., counter clockwise)represented by arrow B. It should be understood that the two permanentmagnets 1134, 1136 may rotate in the counter clockwise direction whilethe internal magnet 1064 may rotate in the clockwise direction. Rotationof the two permanent magnets 1134, 1136 and the internal magnet 1064continues as represented by the 180° and 270° orientations asillustrated in FIGS. 13C and 13D. Rotation continues until the startingposition (0°) is reached again.

During operation of the external adjustment device 1130, the permanentmagnets 1134, 1136 may be driven to rotate the internal magnet 1064through one or more full rotations in either direction to increase ordecrease distraction of the distraction device 140 as needed. Of course,the permanent magnets 1134, 1136 may be driven to rotate the internalmagnet 1064 through a partial rotation as well (e.g., ¼, ⅛, 1/16, etc.).The use of two magnets 1134, 1136 is preferred over a single externalmagnet because the driven magnet 1064 may not be oriented perfectly atthe start of rotation, so one external magnet 1134, 1136 may not be ableto deliver its maximum torque, which depends on the orientation of theinternal driven magnet 1064 to some degree. However, when two (2)external magnets (1134, 1136) are used, one of the two 1134 or 1136 willhave an orientation relative to the internal driven magnet 1064 that isbetter or more optimal than the other. In addition, the torques impartedby each external magnet 1134, 1136 are additive. In prior artmagnetically driven devices, the external driving device is at the mercyof the particular orientation of the internal driven magnet. Thetwo-magnet embodiment described herein is able to guarantee a largerdriving torque—as much as 75% more than a one-magnet embodiment in theAIS application—and thus the internal driven magnet 1064 can be designedsmaller in dimension, and less massive. A smaller internal driven magnet1064 will have a smaller image artifact when performing MRI (MagneticResonance Imaging), especially important when using pulse sequences suchas gradient echo, which is commonly used in breast imaging, and leads tothe largest artifact from implanted magnets. In certain configurations,it may even be optimal to use three or more external magnets, includingone or more magnets each on two different sides of the body (for examplefront and back).

While the external adjustment device 1130 and adjustment device 232 havegenerally been described as functioning using rotational movement ofdriving elements (i.e., magnetic elements) it should be understood thatcyclic or non-rotational movement can also be used to drive or adjustthe distraction device 140. For instance, cyclic movement of drivenmagnet 640, magnetic element 218, internal magnet 1064, internallylocated driven magnet 1402, cylindrical magnet 394, hollow magnet 564,magnet 576, magnet 262, magnets 618, 620, and magnet 1302 may be used todrive or adjust the distraction device 140. Cyclic movement includespartial rotational movement (e.g., rotational movement that is less thana full revolution). Cyclic movement of one or more of the externalmagnets 624, 626, 1134, 1136 may also be employed.

In still another alternative, linear or sliding motion back-and-forthmay also be used to adjust the distraction device 140. In this regard, asingle magnet located internal to the patient that slides back-and-forthon a slide or other base can be used to adjust the distraction device140 using a ratchet-type device. The sliding, internal magnet may bedriven via one or more externally-located permanent/electromagnets thatslides or moves laterally (or moves the magnetic field) in a similarback-and-forth manner. Rotational movement of the externally-locatedmagnetic element(s) may also be used to drive the internal magnet. Theinternal magnet may alternatively be able to rotate back-and-forth, thusadjusting the distraction device 140 using a ratchet-type device.

In still another alternative, permanent magnets may be located on apivoting member that pivots back and forth (like a teeter-totter) abouta pivot point. For example, a first permanent magnet having a North poleoriented in a first direction may be located at one end of the pivotingmember while a permanent magnet having a South pole oriented in thefirst direction is located at the other end of the pivoting member. Aratchet-type device may be used to translate the pivoting movement intolinear movement that can actuate or adjust the distraction device 140.The first and second internally-located permanent magnets may be drivenby one or more externally located magnetic elements (either permanent orelectromagnets). External motion of the electric field by linear or evenrotational movement may be used to the drive the pivoting member.

Two different models of internal driven magnets were constructed, eachfrom a different Neodymium-Iron-Boron Grade. Both magnets had identicaldimensions (0.275″ diameter, 0.395″ long). One magnet was a grade ofapproximately N38 and the other was a grade of N50. Both magnets wereapproximately 2.9 grams in mass. A 1″ diameter cylindrical permanentmagnet (grade N50 Neodymium-Iron-Boron) was attached to a torque gaugeand the peak coupling torque (in inch-ounces) between it and each of theinternal drive magnet models was measured for three different angularorientations for the cylindrical permanent magnet, in relation to theinternal driven magnet. All magnets were two pole (as in FIGS. 13A-13D).Each of the internal driven magnets was tested individually. Theorientation was either 0° (worst case coupling torque), 45° or 90° (bestcase coupling torque). The data for a one inch air gap (separationbetween magnets) is listed below in Table I below. A one (1) inch airgap is an expected worst case separation in the clinical application ofadolescent idiopathic scoliosis. The effect of using two external 1″diameter permanent magnets (as in FIGS. 13A-13D) is shown by addition ofthe values for the worst case (0°) and best case (90°) orientations.

TABLE 1 Peak Coupling Torque (oz-in) at 1″ Air Gap 0° 45° 90° Twoexternal orientation orientation orientation magnets (0° Internal ofsingle of single of single orientation + driven external externalexternal 90° magnet magnet magnet magnet orientation) Grade 38 1.37 1.922.47 3.84 (approx) Grade 50 1.70 7.04 2.80 4.50

It can clearly seen at the additive use of two external permanentmagnets, especially if synchronized in the orientation shown in FIGS.13A-13D, delivers significantly more torque than a single externalmagnet in any orientation. For the data generated using the 50 gradeinternal driven magnet, the peak coupling torque using two externalpermanent magnets was 4.50 ounce-inches, 60.7% greater than a singleexternal permanent magnet oriented at the ideal 90° in relation to theinternal driven magnet, and 164.7% greater than a single externalpermanent magnet oriented at the worst case 0°. This significantincrease in torque achieved by using two external permanent magnets,makes it possible to incorporate an especially small internal drivenmagnet (e.g., less than three grams) into the design of the scoliosistreatment implant, or any implant for manipulating one or more bones ora portion of the skeletal system. For example, the use of two externalpermanent magnets may impart a coupling torque of at least 3.0inch-ounces to the internal magnet at a separation distance of around1.0 inches.

In a gradient echo MRI scan of the breast in a 1.5 Tesla MRI scannerusing standard breast imaging coils, a 2.9 gram N50 grade magnet havinga 0.275 inch diameter and 0.295″ length implanted in the mid-thoraxcreates an MRI artifact which is small enough to allow full imaging ofthe breasts. Using the dual 1″ diameter external permanent magnets 1134,1136 as for the external adjustment device 1130, and using the grade 50for the internal driven magnet 1064 having a mass of 2.9 grams, the 4.50ounce-inch torque delivered to the magnet will turn a 80 threads perinch lead screw mounted on ball bearing in a sufficient manner to applya distraction force of approximately 11 pounds. If a 4:1 reductionplanetary gear set is incorporated into the design—for example, betweenthe internal driven magnet 1064 and the lead screw 226—then adistraction force of approximately 44 pounds may be delivered. In thesystem contemplated by this invention, in which several gradualnon-invasive adjustments are made, distraction forces on this order (40to 45 pounds) will be sufficient. In fact, the slip clutch 244 caneither be adjusted in the fabrication of the scoliosis implant or can beadjusted by the implanting physician, so that the slip clutch 244 slipsat either a maximum threshold torque (to save the materials of theimplant from being damaged or pulling out of the bone by too high adistraction force) or at desired threshold torque (at which the desireddistraction force is generated).

The maximum threshold torque corresponds to a critical distractionforce, and the desired threshold torque corresponds to a desireddistraction force. A critical distraction force may correspond to aforce at which anchors such as hooks or screws may cause damage to thebone. For example, one critical distraction force is 100 pounds, whichin one embodiment of the invention corresponds to a critical thresholdslip torque of 41.7 ounce-inches (if no gear reduction, and a 80 threadsper inch lead screw is used), 10.4 ounce-inches (if a 4:1 gear reductionand a 80 threads per inch lead screw is used) or 2.6 ounce-inches (if a16:1 gear reduction and a 80 threads per inch lead screw is used).Similarly, one desired distraction force is 45 pounds, which in oneembodiment of the invention corresponds to a desired threshold sliptorque of 18.75 ounce-inches (if no gear reduction and a 80 threads perinch lead screw is used) or 4.69 ounce-inches (if a 4:1 gear reductionand a 80 threads per inch lead screw is used). If a desired distractionforce is 20 pounds, then in one embodiment of the invention thiscorresponds to a desired threshold slip torque of 8.33 ounce-inches (ifno gear reduction and a 80 threads per inch lead screw is used) or 2.08ounce-inches (if a 4:1 gear reduction and a 80 threads per inch leadscrew is used). In one aspect, the desired threshold distraction isbetween 2 inch-ounces and 42 inch-ounces. In another aspect, the desiredthreshold distraction is between 2 inch-ounces and 19 inch-ounces. Instill another aspect, the desired threshold distraction is between 2inch-ounces and 8.5 inch-ounces.

Other distraction devices have been proposed which incorporate a smallimplantable motor to effect the distraction. The 2.9 gram cylindricalmagnet 1064 described as part of the present invention is significantlysmaller than the smallest motor which would be feasible in thedistraction application, considering torque requirements, etc. Inaddition, the cost of the magnet 1064 is significantly less than that ofa micromotor. The magnet 1064 is also very reliable in relation to amicromotor. The main possible failure would be the loss of the magneticfield, however the inventors have demonstrated that the inventive 2.9gram magnet 1064 can be placed into the center of a 3.0 Tesla MRI magnetwithout a significant loss in magnetism. It can also be exposed totemperatures in excess of those used in steam sterilization, forexample, without a significant loss of magnetism. Generally, theinternal magnet 1064 should be grade N30 or higher, or even grade N48 orhigher. While the 2.9 gram cylindrical magnet 1064 has the advantage ofbeing particularly small, in other embodiments, the cylindrical magnet1064 may have a weight of less than about 10 grams or less than about6.0 grams. Similarly, the first and second external magnets 1134, 1136may be a rare earth permanent magnets such as, for instance.Neodymium-Iron-Boron. In addition, the first and second external magnets1134, 1136 may be grade N30 or higher, or even grade N48 or higher.

FIG. 14 illustrates a system 1076 according to one aspect of theinvention for driving the external adjustment device 1130. FIG. 14illustrates the external adjustment device 1130 pressed against thesurface of a patient 1077 (torso face down shown in cross-section). Theportion of the distraction device 140 containing the internal drivenmagnet 1064 is illustrated. The permanent magnet (e.g., the drivenmagnet 1064) that is located within the distraction device 140 locatedinside the patient 1077 is magnetically coupled through the patient'sskin and other tissue to the two external magnets 1134, 1136 located inthe external adjustment device 1130. As explained herein, one rotationof the external magnets 1134, 1136 causes a corresponding singlerotation of the driven magnet 1064 located within the distraction device140. Turning the driven magnet 1064 in one direction causes thedistraction device 140 to lengthen, or increase distraction force whileturning in the opposite direction causes the distraction device 140 toshorten, or decrease distraction force. Changes to the distractiondevice 140 are directly related to the number of turns of the drivenmagnet 1064.

The motor 1132 of the external adjustment device 1130 is controlled viaa motor control circuit 1078 operatively connected to a programmablelogic controller (PLC) 1080. The PLC 1080 outputs an analog signal tothe motor control circuit 1078 that is proportional to the desired speedof the motor 1132. The PLC 1080 may also select the rotational directionof the motor 1132 (i.e., forward or reverse). In one aspect, the PLC1080 receives an input signal from a shaft encoder 1082 that is used toidentify with high precision and accuracy the exact relative position ofthe external magnets 1134, 1136. For example, the shaft encoder 1082 maybe an encoder 1175 as described in FIGS. 10-11. In one embodiment, thesignal is a pulsed, two channel quadrature signal that represents theangular position of the external magnets 1134, 1136. The PLC 1080 mayinclude a built in screen or display 1081 that can display messages,warnings, and the like. The PLC 1080 may optionally include a keyboard1083 or other input device for entering data. The PLC 1080 may beincorporated directly into the external adjustment device 1130 or it maybe a separate component that is electrically connected to the mainexternal adjustment device 1130.

In one aspect of the invention, a sensor 1084 is incorporated into theexternal adjustment device 1130 that is able to sense or determine therotational or angular position of the driven magnet 1064. The sensor1084 may acquire positional information using, for example, sound waves,ultrasonic waves, light, radiation, or even changes or perturbations inthe magnetic or electromagnetic field between the driven magnet 1064 andthe external magnets 1134, 1136. For example, the sensor 1084 may detectphotons or light that is reflected from the driven magnet 1064 or acoupled structure (e.g., rotor) that is attached thereto. For example,light may be passed through the patient's skin and other tissue atwavelength(s) conducive for passage through tissue. Portions of thedriven magnet 1064 or associated structure may include a reflectivesurface that reflects light back outside the patient as the drivenmagnet 1064 moves. The reflected light can then be detected by thesensor 1084 which may include, for example, a photodetector or the like.

In another aspect, the sensor 1084 may operate on the Hall effect,wherein two additional magnets are located within the implantableassembly. The additional magnets move axially in relation to each otheras the driven assembly rotates and therefore as the distractionincreases or decreases, allowing the determination of the current sizeof the restriction device.

In the embodiment of FIG. 14, the sensor 1084 is a microphone disposedon the external adjustment device 1130. For instance, the microphonesensor 1084 may be disposed in the recessed portion 1174 of the externaladjustment device 1130. The output of the microphone sensor 1084 isdirected to a signal processing circuit 1086 that amplifies and filtersthe detected acoustic signal. In this regard, the acoustic signal mayinclude a “click” or other noise that is periodically generated byrotation of the driven magnet 1064. For example, the driven magnet 1064may click every time a full rotation is made. The pitch (frequency) ofthe click may differ depending on the direction of rotation. Forexample, rotation in one direction (e.g., lengthening) may produce a lowpitch while rotation in the other direction (e.g., shortening) mayproduce a higher pitch signal (or vice versa). The amplified andfiltered signal from the signal processing circuit 1086 can then pass tothe PLC 1080.

During operation of the system 1076, each patient will have a number orindicia that correspond to the adjustment setting or size of theirdistraction device 140. This number can be stored on an optional storagedevice 1088 (as shown in FIG. 14) that is carried by the patient (e.g.,memory card, magnetic card, or the like) or is integrally formed withthe distraction device 140. For example, a RFID tag 1088 implantedeither as part of the system or separately may be disposed inside thepatient (e.g., subcutaneously or as part of the device) and can be readand written via an antenna 1090 to update the current size of thedistraction device 140. In one aspect, the PLC 1080 has the ability toread the current number corresponding to the size or setting of thedistraction device 140 from the storage device 1088. The PLC 1080 mayalso be able to write the adjusted or more updated current size orsetting of the distraction device 140 to the storage device 1088. Ofcourse, the current size may recorded manually in the patient's medicalrecords (e.g., chart, card or electronic patient record) that is thenviewed and altered, as appropriate, each time the patient visits his orher physician.

The patient, therefore, carries their medical record with them, and if,for example, they are in another location, or even country, and need tobe adjusted, the RFID tag 1088 has all of the information needed.Additionally, the RFID tag 1088 may be used as a security device. Forexample, the RFID tag 1088 may be used to allow only physicians toadjust the distraction device 140 and not patients. Alternatively, theRFID tag 1088 may be used to allow only certain models or makes ofdistraction devices to be adjusted by a specific model or serial numberof external adjustment device 1130.

In one aspect, the current size or setting of the distraction device 140is input into the PLC 1080. This may be done automatically or throughmanual input via, for instance, the keyboard 1083 that is associatedwith the PLC 1080. The PLC 1080 thus knows the patient's starting point.If the patient's records are lost, the length of the distraction devicemay be measured by X-ray and the PLC 1080 may be manually programmed tothis known starting point.

The external adjustment device 1130 is commanded to make an adjustment.This may be accomplished via a pre-set command entered into the PLC 1080(e.g. “increase distraction displacement of distraction device 140 by0.5 cm” or “increase distraction force of distraction device 140 to 20pounds”). The PLC 1080 configures the proper direction for the motor1132 and starts rotation of the motor 1132. As the motor 1132 spins, theencoder 1082 is able to continuously monitor the shaft position of themotor directly, as is shown in FIG. 14, or through another shaft orsurface that is mechanically coupled to the motor 1132. For example, theencoder 1082 may read the position of markings 1177 located on theexterior of a pulley 1162C like that disclosed in FIG. 10. Everyrotation or partial rotation of the motor 1132 can then be counted andused to calculate the adjusted or new size or setting of the distractiondevice 140.

The sensor 1084, which may include a microphone sensor 1084, may bemonitored continuously. For example, every rotation of the motor 1132should generate the appropriate number and pitch of clicks generated byrotation of the permanent magnet inside the distraction device 140. Ifthe motor 1132 turns a full revolution but no clicks are sensed, themagnetic coupling may have been lost and an error message may bedisplayed to the operator on a display 1081 of the PLC 1080. Similarly,an error message may be displayed on the display 1081 if the sensor 1084acquires the wrong pitch of the auditory signal (e.g., the sensor 1084detects a shortening pitch but the external adjustment device 1130 wasconfigured to lengthen).

FIGS. 15 through 30 schematically illustrate an acoustic indicatorhousing 1304 and a driven magnet 1302 as the driven magnet 1302 isrotated in both the clockwise directions (arrow A) and counter-clockwisedirections (arrow B). It should be understood that while a descriptionis given with respect to driven magnet 1302, the acoustic sensingfeatures may also apply to magnetic element 218 of FIGS. 6C-6G, theinternal magnet 1064 of FIGS. 13A-13D, 14, the internally located drivenmagnet 1402 of FIG. 35, cylindrical magnet 394 of FIGS. 41, 42, and 44,the hollow magnet 564 of FIG. 48, magnet 576 of FIG. 50, magnet 262 ofFIG. 53, and magnets 618, 620 of FIG. 51, magnet 640 of FIG. 52, or evenmagnetic member 200 of FIG. 6B (these various implementations of drivenmagnets may be referred to, in some instances, as magnetic elements).The acoustic indicator housing 1304 is illustrated in an annularconfiguration with respect to the circumference of the driven magnet1302, but an alternative relationship is contemplated, for examplewherein the outer diameter of the acoustic indicator housing 1304 issubstantially the same as the outer diameter of the driven magnet 1302,and they are oriented with an end-to-end axial relationship instead ofan annular relationship. Acoustic indicator housing 1304 is one possibleembodiment of the acoustic housing 222 of FIG. 6C and FIG. 6D. Theacoustic indicator housing 1304 is used to create an acoustic signal(e.g., a click) that can be used to count rotational movement of thedriven magnet 1302 and also determine its rotational direction. Anacoustic signal (i.e., sound) is generated when a magnetic ball 1306strikes either a first impact surface 1308 or a second impact surface1310. FIGS. 15-22 illustrate rotation of the driven magnet 1302 in theclockwise direction (arrow A) while FIGS. 23-30 illustrate rotation ofthe driven magnet 1302 in the counter-clockwise direction (arrow B).When the driven magnet 1302 is rotated in the clockwise direction, themagnetic ball 1306 strikes the first impact surface 1308 two times (2×)per full rotation, with the first impact surface 1308 producing soundwith a first amplitude and/or frequency. When the driven magnet 1302 isrotated in the counter-clockwise direction, the magnetic ball 1306strikes the second impact surface 1310 two times (2×) per full rotation,with the second impact surface 1310 producing sound with a secondamplitude and/or frequency.

As illustrated in FIGS. 15-30, the first impact surface 1308 is thinnerthan the second impact surface 1310, and thus, the first impact surface1308 is configured to resonate at a higher frequency than the secondimpact surface 1310. Alternatively, the difference in frequency can beachieved by making the first impact surface 1308 from a differentmaterial than the second impact surface 1310. Alternatively, theamplitude of acoustic signal generated by the magnetic ball 1306 hittingthe first and second impact surfaces 1308, 1310 may be used todiscriminate rotational direction. For example, clockwise rotation mayproduce a relatively loud click while counter-clockwise rotation mayproduce a relatively quiet click.

The magnetic ball 1306 is made from a magnetic material, for example 400series stainless steel. The magnetic ball 1306 is attracted to both asouth pole 1314 of the driven magnet 1302 and a north pole 1316 of thedriven magnet 1302. As seen in FIG. 15, the driven magnet 1302 begins torotate in the clockwise direction (arrow A). As pictured, the startingpoint of the magnetic ball 1306 is adjacent to the north pole 1316 ofthe magnet 1302. As seen in FIG. 16, as the magnet 1302 rotates, themagnetic ball 1306 follows the north pole 1316. This continues until, asshown in FIG. 17, the magnetic ball 1306 is stopped by the second impactsurface 1310. Now, as seen in FIG. 18, the magnetic ball 1306 is trappedagainst the second impact surface 1310, while the driven magnet 1302continues to rotate. The magnetic ball 1306 may roll at this point, butit is forced against the second impact surface 1310 by its attraction tothe north pole 1316 of the magnet 1302, until the south pole 1314becomes substantially closer to the magnetic ball 1306 as shown in FIG.19, at which point the magnetic ball 1306 accelerates towards the firstimpact surface 1308 in the direction of arrow a, thereby hitting it (asseen in FIG. 20) and creating an acoustic signal or sound having agreater intensity than when the magnetic ball 1306 was stopped by thesecond impact surface 1310. Now, as the driven magnet 1302 continues toturn, the magnetic ball 1306 follows the south pole 1314 of the drivenmagnet 1302 as seen in FIG. 21, and continues to follow the south pole1314 until the magnetic ball 1306 is stopped by the second impactsurface 1310 as seen in FIG. 22.

FIGS. 23-30 illustrate the acoustic mechanism being activated bycounter-clockwise rotation of the driven magnet 1302. In this process,the first impact surface 1308 serves to stop the magnetic ball 1306, andthe magnetic ball 1306 accelerates and impacts the second impact surface1310, creating a different acoustic signal. For example, the differentacoustic signal may include a louder signal or a signal with a differentfrequency (e.g., pitch). In FIG. 23, the driven magnet 1302 begins torotate in the counter-clockwise direction (arrow B). As illustrated, thestarting point of the magnetic ball 1306 is adjacent the south pole 1314of the magnet 1302. As seen in FIG. 24, as the magnet 1302 rotates, themagnetic ball 1306 follows the south pole 1314. This continues until, asshown in FIG. 25, the magnetic ball 1306 is stopped by the first impactsurface 1308. As seen in FIG. 25, the magnetic ball 1306 is trappedagainst the first impact surface 1308, while the driven magnet 1302continues to rotate. The magnetic ball 1306 may roll at this point, butit is forced against the first impact surface 1308 by its attraction tothe south pole 1314 of the magnet 1302, until the north pole 1316becomes closer to the magnetic ball 1306 as shown in FIG. 26, at whichpoint the magnetic ball 1306 accelerates towards the second impact plate1310 in the direction of arrow p, thereby hitting it (as seen in FIG.27) and creating an acoustic signal or sound having a greater intensitythan when the magnetic ball 1306 was stopped by the first impact surface1308. Now as seen in FIG. 28, as the magnet 1302 continues to turn, themagnetic ball 1306 follows the north pole 1316 of the magnet 1302, andcontinues to follow the north pole 1316 (FIG. 29) until the magneticball 1306 is stopped by the first impact surface 1308 as illustrated inFIG. 30.

It can be appreciated that each turn of the magnet 1302 creates two (2)relatively loud strikes, which can be detected by a non-invasive,external device comprising a sonic sensor, for example, a microphone(e.g., sensor 1084 in FIG. 14). If, for example, the magnet 1302 isturning a 0-80 lead screw (e.g., lead screw 226) to adjust thedistraction device 140), then each turn represents 1/80 of an inch inthe distraction displacement, and thus each half turn represents 1/160of an inch, or 0.00625″. If there is gear reduction at the output of themagnet 1302, for example 4:1, then a full turn represents 1/320 of aninch and each half turn represents 1/640 of an inch. Therefore, acousticsensing of this nature allows for very precise control of adjustment ofthe distraction device 140. If the speed is too high, the sensor canalternatively be programmed to sense only specific turns. Alternatively,a secondary magnet may be disposed on the post gear reduction portion ofthe torque transmission system, so that the number of turns to sense arefewer in number and less frequent.

It can also be appreciated that the acoustic signal or sound made by thestrike due to the acceleration of the magnetic ball 1306 against thefirst impact surface 1308 during clockwise rotation of the magnet 1302will contain a different frequency spectrum than the acoustic signal orsound made by the strike due to the acceleration of the magnetic ball1306 against the second impact surface 1310 during counter-clockwiserotation of the magnet 1302. As one example, the acoustic sensor 1084illustrated in FIG. 14 may provide a relatively simple, low-cost devicein which the direction of the rotation (i.e., increasing distraction vs.decreasing distraction) can be automatically identified. Further, theacoustic sensor 1084 is able to determine the exact number of halfrotations in each direction.

The acoustic sensor 1084 may be operatively integrated with aprogrammable logic controller (PLC) such as the PLC 1080 describedherein. In this regard, the exact distraction length of the distractiondevice 140 can be determined. The PLC 1080 is able to identify thedirection of rotation via the frequency of sound, and then change thedirection of rotation if this is not the desired direction. The PLC 1080is also able to count the number of half rotations until amount ofrestriction is achieved. If there is any slip between the magnets 1134,1136 of the external device 1130 and the driven magnet 1302, the PLC1080 will not detect the acoustic signal and thus will not count theseas rotations.

There may be cases in which the medical personnel performing thenon-invasive adjustment is not aware which direction of rotation of theexternal device magnets 1134, 1136 will cause increased distraction andwhich will cause decreased distraction. The PLC 1080, however, will beable to immediately identify the correct direction of rotation by thedetected frequency.

For example, FIG. 31 illustrates the sound 1320 detected fromcounter-clockwise rotation of the magnet 1302 and FIG. 32 illustratesthe sound 1324 detected from clockwise rotation of the magnet 1302.There may be additional background acoustic signals or noise 1328created by, for example, the sound of the motor 1132 of the externaldevice 1130. In both rotation directions, the acoustic “clicks” 1320 and1324 look very similar to each other. However, by analyzing thefrequency spectrum of the clicks, one is able to discern differencesbetween clockwise and counter-clockwise rotation of the magnet 1302. Asseen in FIG. 33, the frequency spectrum for the counter-clockwiserotation is centered at about 14 kHz, while the spectrum for clockwiserotation (FIG. 34) is centered at about 18 kHz. This shift or change incenter frequency can be used as a basis for determining the absoluterotational direction of the magnet 1302.

FIG. 35 illustrates a system 1400 for driving an internally locateddriven magnet 1402 of a distraction device 140 via an external device1406 using a feedback device. One or more implanted driven magnets 1402are coupled magnetically through the skin 1404 of a patient 1408 to oneor more external drive magnets 1410. A rotation or movement of theexternal drive magnets 1410 causes an equal rotation of the drivenmagnet(s) 1402. Turning the driven magnet(s) 1402 in one direction 1412causes the distraction device 1414 to increase distraction while turningthe driven magnet(s) 1402 in the opposite direction causes thedistraction device 1414 to decrease distraction. Changes to thedistraction device 1414 distraction distance or distraction force dependupon the number of turns by the one or more drive magnets 1410.

The drive magnets 1410 are rotated by the external device 1406, whichhas an electric gear motor 1416 which is controlled by a programmablelogic controller (PLC) 1418. The PLC 1418 outputs an analog signal 1420to a motor drive circuit 1422 which is proportional to the motor speeddesired. The PLC 1418 receives an analog signal 1424 from the motordrive circuit 1422 that is proportional to the current draw of themotor. The gear motor's 1416 current consumption is proportional to itsoutput torque. An electronic torque sensor may be used for this purpose.The measured current draw may be used to monitor the change in outputtorque.

The PLC 1418 receives a pulsed input signal 1426 from an encoder 1428that indicates the angular position of the drive magnets 1410. The PLC1418 controls a spring loaded braking system 1430 that automaticallystops the drive magnet 1410 if there is a loss of electrical power orother emergency.

A slip clutch 1432 is included between the gear motor 1416 and the drivemagnet 1410 to prevent the gear motor 1416 from over torqueing thedriven magnet 1402 and potentially damaging the distraction device 140,for example, if the distraction device 140 does not have its own slipclutch. The PLC 1418 has a built in screen 1434 to display messages anda keypad 1436 for entering data. External push button switches andindicator lights may be incorporated for user comfort and ease of use.

The motor current (output torque) is monitored continuously whenever thedevice is turning. If the motor current exceeds the maximum allowablecurrent (based on safety requirements of the device components and/orpatient tissue) the gear motor 1416 is stopped and the brake 1430 isapplied. This can be done both in software and hardware. The mechanicalslip clutch 1432 also prevents over torqueing of the device. Anexemplary threshold torque is 5.0 ounce-inches.

In one embodiment, each patient will have a number that corresponds tothe distraction displacement of their particular distraction device1414. A distracted device 1414 will have a number such as 5.0 cm for itsdistraction displacement and a fully non-distracted device will have anumber such as 0.0 cm.

This number can be stored on an electronic memory card 1438 that thepatient 1408 carries. The PLC 1418 can read the current number from thememory card 1438 and update the number after adjustment. The patient'snumber can be recorded manually in the patient's chart and kept at thephysician's office or printed on an information card that the patientcarries. Alternatively, the information can be stored on and read froman RFID chip implanted in the patient.

The patient's number is first entered into the PLC 1418 so it knows thepatient's starting point. If the patient's records are completely lost,the system can always have a new setting manually input based on anX-ray image determination of the distraction displacement of therestriction device 1414.

A physician may adjust the distraction device 1414 several ways. Anabsolute move to a new distraction displacement (or force) may beentered directly. For example, a patient 1408 currently at 2.00 cmdistraction displacement may need to be adjusted to 2.50 cm. Thephysician simply enters the new distraction displacement and presses a‘GO’ button. The physician may prefer a relative (incremental) move fromthe current distraction displacement. Each press of a button will causethe device to increase or possible decrease a fixed amount, say 0.20 cmof distraction displacement, or 0.02 cm. In another aspect, there may beprovided increase and decrease buttons which increase/decrease thedistraction of the distraction device 1414 as long as the button isheld. It should be noted that the displacement of distraction is arelative term, and that the force gauge disclosed in this invention maybe the preferred manner to adjust distraction, instead of a dimensionalmanner. Further, the PLC 1418 may automatically adjust the externaldevice 1406 to reach the desired final distraction force or length basedat least in part on a response generated by a feedback device. Theparticular feedback device may be any number of devices described hereinincluding strain or force gauge feedback, acoustic feedback, opticalfeedback, motor current and the like.

Once the external device 1406 is commanded to move, the PLC 1418 slowlyramps up the speed of the gear motor 1416 while monitoring the motorcurrent (torque). A known minimum drive torque must be present forverification that the magnetic coupling to the restriction device islocked and not slipping. This can be monitored with, for example, theacoustic feedback system. The minimum torque value can be a curve thatis stored in the PLC 1418 that is based on the amount of distraction,the direction of movement (increasing/decreasing), even the model numberor serial number of the distraction device 1414.

Also, if a sudden torque reversal is detected by the PLC 1418, a sliphas occurred. As the like magnet poles (North-North & South-South) whichare repelling slip past each other, they are attracted to the adjacentopposite poles (North-South & South-North). This causes a momentaryreversal of drive torque. This torque reversal can be detected by thePLC 1418. If a slip occurs, the PLC 1418 can subtract the appropriateamount from the move. If too many consecutive slips occur, the PLC 1418can stop and display a message.

As the drive magnet 1410 rotates, revolutions and fractions ofrevolutions are counted by the PLC 1418 and converted to changes in thedistraction. Once the move is complete, the PLC 1418 stops the gearmotor 1416 and applies the brake 1430. It should be understood that thefeedback devices mentioned above is applicable to the external device,and to many other types of magnetic drives with the exception of nearbyor proximally-located electromagnetic coils which do not have a motor.

Any of the compatible configurations of a distraction device/adjustmentmechanism/external adjustment device are contemplated to be combinableas alternative embodiments to those specifically described herein. Inaddition, the mechanical mechanism of the distraction device can beachieved by any of the designs and methods by using a rotating driveshaft, or by a tension/compression member. In other words, rotation canbe done only to proximal assemblies or assemblies within the distractiondevice, which then, through gearing, cause longitudinal shortening orlengthening of a wire or cable, which pulls tension on a belt or rod tocause the distraction device to increase or decrease distraction(distance or force).

FIG. 36 illustrates an embodiment of a distraction device 314 implantedwithin a patient and fixated at its upper end 315 and lower end 317 tothe patient's spine 300. The illustrated example of the spine 300includes the particular thoracic and lumbar vertebrae that typicallyencompass a scoliotic curve, for example the curve of a patient withadolescent idiopathic scoliosis. The T3 through T12 thoracic vertebrae,303, 304, 305, 306, 307, 308, 309, 310, 311, 312, respectively and theL1 through L3 vertebrae, 291, 292, 293 are depicted in FIG. 36, not in asevere scoliotic condition, but in a very slight residual curve thatrepresents a modest curve that has been partially or completelystraightened during the implantation procedure. Each vertebra isdifferent from the other vertebra by its size and shape, with the uppervertebra generally being smaller than the lower vertebra. However,generally, the vertebrae have a similar structure and include avertebral body 316, a spinous process 318, 320, laminae 326, transverseprocesses 321, 322 and pedicles 324. In this embodiment, the distractiondevice 314 includes a distraction rod 328 which is adjustable(lengthwise) via a coupled adjustable portion 330. The distractiondevice 314 is fixated to the spine 300 via a clamp 342 at the upper endof the distraction rod 328. In FIG. 36, the clamp 342 is secured aroundthe transverse process 321 of the T4 vertebra 304. Alternatively, theclamp 342 may be secured around an adjacent rib (not shown) or ribfacet. In still another alternative, the clamp may be replaced by alaminar and pedicle hook system, or pedicle screw system. FIG. 37illustrates one such alternative embodiment in which a distractiondevice 314 includes one or more laminar hooks 346 that are used tosecure an upper end 315 of the distraction device 314 to the spine (notshown). The lower end 317 of the distraction device is secured to thespine using one or more pedicle hooks 348.

Referring back to FIG. 36, the distraction device 314 is illustrated asbeing fixated to the spine 300 with a pedicle screw system 331comprising a connecting rod 332 and two toe clamps 338, 340. Thisparticular embodiment comprises a magnetic adjustment device 344 whichis spaced from the adjustable portion 330 via a transmission cable 345.

Turning to FIG. 38, more detail of the pedicle screw system 331 isshown. The pedicle screw 349 passes through a hole in base 350, securingbase to the L1 vertebra 291 (FIG. 36) though its pedicle (left pediclein this case). Locking screw 334 can be loosened to adjust the angle αof the connecting rod 332, and then locking screw 334 can be tightenedso that toe clamp 338 securely holds connecting rod 332 in place withoutfurther rotation. The second toe clamp 340 is adjusted in the same way,by tightening locking screw 336. Because a scoliotic spine is alsorotated (usually the center section is rotated to the right in AISpatients), the non-fusion embodiment presented here allows de-rotationof the spine 300 to happen naturally, because there is no fixation atthe middle portion 319 of the distraction device 314.

In order to further facilitate this de-rotation, the distraction device314 allows for free rotation at its ends. For example, turning to FIG.39, the adjustable portion 330 is attached to the connecting rod 332 viaa ball joint 382. The end of the connecting rod 332 has a substantially180° curve which allows it to meet the adjustable portion 330 along thesame axis 383. The extreme end of the connecting rod 332 comprises astem 386 and a ball 384. A mount 360 is disposed at the end of theadjustable portion 330 and has a partial spherical internal contour 361to mate with the ball 384, and allow for free rotation. It may alsoallow for polyaxial motion. It should be noted that distraction rod 328may be precurved with the typical shape of a normal saggital spine, butit should also be noted that the curve may be slightly different thanstandard scoliosis fusion instrumentation, because in the non-fusionembodiment described herein, the distraction device 314 is not flushwith the spine but rather is placed either subcutaneous or sub-fascial,and thus is not below the back muscles. The only portions of thedistraction device 314 that are designed to be placed below the musclesare the clamp 342 and the portion of the distraction rod 328 immediatelyadjacent the clamp 342, the pedicle screw system 331 and the connectingrod 332. Thus, FIG. 36 illustrates an embodiment in which the bulk ofthe hardware associated with the distraction device 314 is placed overthe muscle. It should be understood, however, that in alternativeconfigurations, any other part of the entire implantable embodiment maybe placed under the muscle (i.e., sub-muscular). It should beappreciated that a much smaller amount of muscle needs to be dissectedduring the procedure in comparison with current fusion procedures. Thiswill allow for a much shorter procedure, much less blood loss, muchquicker recovery, and less time in the hospital/less risk of infection.Further, it may be desirable to produce the “J” curve of the connectingrod 332 or the “S” curve of connecting rod 323 of FIG. 37 with flangesor ribs at their highest stress points in order to increase theirdurability in demanding implant conditions.

FIG. 40 and FIG. 41 illustrate one embodiment of a remotely-locatedmagnetic adjustment device 344 that enables adjustment of thedistraction device 314 from a location that is remote from theadjustable portion 330. As explained below, the adjustable portion 330is operatively coupled to the magnetic adjustment device 344 via atransmission cable 345. For example, the magnetic adjustment device 344may be placed subcutaneously in the buttocks area or even the abdominalarea. Alternatively, the magnetic adjustment device 344 may be locatedintegral to the adjustable portion 330. In its remote configuration,however, the magnetic adjustment device 344 (depicted in FIG. 41 withoutits protective outer cover) includes a worm 390 and a cylindrical magnet394 fixedly secured inside the worm 390. The cylindrical magnet 394 ispreferably magnetized radially as illustrated in FIG. 42. Activation ofan external adjustment device (e.g., external adjustment device 1130)causes the cylindrical magnet 394 and worm 390 to turn. The worm 390contains threads about its exterior surface and engages with a rotatablegear 392 which, in turn, is operatively coupled to a spool 396. Thespool 396 includes a groove or the like about its periphery in which acable 362 is disposed. During operation of the device, rotationalmovement of the cylindrical magnet 394 causes rotation of the gear 392that, in turn, causes rotation of the spool 396. As the gear 392 turns,the spool 396 winds or unwinds a cable 362 that extends through aprotective sheath 364 located in the elongated transmission cable 345that couples the adjustment device 344 to the adjustable portion 330.Depending on the direction of rotation of the gear 392, the cable 362 iseither tightened or loosened.

Referring to FIG. 41, as the gear 392 turns in direction 388, tension(T) is increased. The opposite end of cable 362 is secured to frame 360by stop 370. In one embodiment, the cable 362 is pulled over firstpulley 354, which turns in a first rotational direction 376. Cable 362then wraps around second pulley 355 (shown in phantom) in the back offrame 360 causing second pulley 355 to turn in second rotationaldirection 377. The cable 362 then wraps around a third pulley 356causing it to turn in third rotational direction 378. After the thirdpulley 356, the cable 362 wraps around a fourth pulley 358, causing itto turn in a fourth rotational direction 380. Second pulley 355 andfourth pulley 358 are rotationally attached to the distraction rod 328via axle 398, and are slidably contained within frame 360 by pin 368which slides in a groove 366.

The combination of the pulleys 354, 355, 356, 358 act as a block andtackle arrangement that amplifies the force applied to the distractionrod 328 in response to an applied tension (T). For instance, a tension(T) that is placed on cable 362 imparts a compressive force (C) on thedistraction rod 328 that is four times as large (i.e., C=4*T). Ofcourse, it should be understood that by driving the cylindrical magnet394 and worm 390 in the opposite direction, the gear 392 causes thespool 396 to unwind, and thus both T and C are decreased.

FIG. 43 illustrates another embodiment of a distraction device 400. Inthis embodiment, hook fixation systems are used to secure to distractiondevice 400 to the patient's spine. The hook fixation system is depictedin an exploded configuration in FIG. 43 and includes hooks 402, 404 (forexample laminar hooks, facet hooks or rib hooks) located on opposingends of the distraction device. The hooks 402, 404 are operativelycoupled to ball joints 406. Each ball joint 406 includes a coupler 405that interfaces with a ball 407 or other substantially spherical memberdisposed at the end of a post 409. The hooks 402, 404 each include arecess 402A, 404A that are dimensioned to receive the post 409 of eachball joint 406. The post 409 is frictionally engaged or locked withrespect to its respective hook 402, 404 using a clamping member 408 andoverlying cap 410. The coupler 405 includes a receiving portion such asan internal threaded portion (not shown) that interfaces with opposingends of the distraction rod 412. Of course, the coupler 405 may besecured to distraction rod 412 in other ways such as, for instance,mounting screws, a bond, weld, or even through the use of a cement orother adhesive material. In this regard, once mounted, both hooks 402,404 are able to articulate about the swivel-action ball joint 406 toaccommodate the changing geometry as the spine is subject to distractionforces.

As seen in FIG. 43, the distraction rod 412 is supplied in a pre-curvedconfiguration, and can be cut to the desired length and bent into acustom configuration to fit the patient's specific anatomy. Typically,the portion that is to be cut would be the end of the distraction rod412 that is located away from the adjustable portion 414. Adjustableportion 414 in this embodiment comprises an offset gearing assembly 415having a cover 416.

FIG. 44 illustrates the offset gearing assembly 415 with the cover 416removed from the adjustable portion 414 in order to better show theinternal components responsible for effecting the distraction forces onthe distraction rod 412. As seen in FIG. 44, a cylindrical magnet 394 isrotationally held by cups 422, 424 and the assembly 415 is free torotate between ball bearings 426, 428 disposed on opposing ends thereof.The cylindrical magnet 394 may include a permanent magnet made out ofthe materials described herein with respect to the other embodiments.The assembly 415 includes a first gear 430 which rotates as the assembly415 is rotated about its axis of rotation. An external adjustment device(e.g., 1130) causes cylindrical magnet 394 to turn in a first rotationaldirection 440 which also causes the first gear 430 to turn in same,first direction 440. The first gear 430 meshes with a second gear 432causing the same to turn in a second rotational direction 442. A thirdgear 434 is secured to the second gear 432 and rotates along with secondgear 432. The third gear 434 meshes with a fourth gear 436, causing itto turn in a third rotational direction 444. The fourth gear 436 issecured to a lead screw 420 which extends longitudinally inside a sleeve418 or jacket. A thrust bearing 438 is provided in a face-to-facearrangement with the fourth gear 436 to reduce frictional forces duringrotation of the lead screw 420. The inner surface of the sleeve 418contains a threaded inner bore (not shown) which extends at least aportion of the length of the sleeve 418. Lead screw 420 is allowed toturn because of a thrust bearing 438 located at end of the lead screw420.

When the lead screw 420 turns in the fourth rotational direction 444 andengages threaded inner bore of sleeve 418, the sleeve 418 begins to movein the distraction direction 446. The sleeve 418 is coupled at one endto the distraction rod 412, and thus, when sleeve 418 and distractionrod 412 are distracted by the offset gearing assembly 415, thedistraction device 400, which is coupled to the spine, imparts anincreased distraction force. If the cylindrical magnet 394 is turned inthe opposite direction, the distraction force is lessened. Because ofboth the gearing and the lead screw thread, a relatively low torque canbe delivered to rotate the cylindrical magnet 394 which, in turn, canimpart a very high distraction force on the sleeve 418, and thus thedistraction rod 412. In one embodiment, the first gear 430 has eight (8)teeth, second gear 432 has eighteen (18) teeth, third gear 434 has ten(10) teeth, and fourth gear 436 has eighteen (18) teeth. The meshing ofthe first gear 430 and second gear 432 has a gear ratio of 18:8 and themeshing of the third gear 434 and fourth gear 436 has a gear ratio of18:10. This creates an overall gear ratio for the offset gearingassembly 415 of 81:10, and thus an output torque to input torque ratioof 4.05. Assuming a typical gear efficiency of 0.90 (due to frictionaleffects in the each of the two gear meshes), a 6.0 ounce-inch torqueapplied to the cylindrical magnet 394 can produce an approximate torqueof 19.7 ounce-inches on the lead screw. A lead screw 420 having adiameter of approximately 3.5 mm (0.138″) and approximately 100 threadsper inch has been measured to have an efficiency of approximately 0.084.Thus, a 6.0 ounce-inch torque applied to the cylindrical magnet 394 willproduce a distraction force of as high as 65 pounds. This assumes anexternal adjustment device 1130 having two external magnets 1134, 1136each having a diameter of approximately two (2) inches.

Returning to FIG. 43, an annular dynamic seal 425 provided at one end ofthe adjustable portion 414 allows the distraction rod 412 to passthrough the end of the adjustable portion 414 without any body fluids ormaterials being able to enter the adjustable portion 414. The interiorof the adjustable portion 414 is thus substantially isolated or sealedoff from the surrounding implant environment. While FIG. 43 illustratesa pair of hooks 402, 404 that are used to secure the distraction device400 to the spine of the patient, it should be understood that otheranchors may be used to affix the ends of the distraction device 400 tothe spine. For example, screws or other fasteners may be used to secureone or both ends of the distraction device 400 to the patient's spine.Typically, screws are used for the lower portion of the distractiondevice 400 while hooks or screws are generally preferred for the upperportion of the distraction device 400. Clamps may also be used to secureone or both ends of the distraction device 400 to the patient's spine.Generally, clamping structures are used to secure the upper portion ofthe distraction device 400 to a rib or transverse process of thesubject.

For example, FIG. 45 illustrates a clamp 450 that can be used to secureone end of the distraction device 400 to a rib or transverse process.The clamp 450 includes an “L-shaped” bracket 452 that is mounted on ashaft 454. The shaft 454 terminates at a swivel joint 456 that providesswiveling movement between a coupler 458 and the clamp shaft 454. Thecoupler 458 is configured to receive one end of the distraction rod 412(e.g., using threads, mounting screw(s), adhesive, cement, laser weld,or the like). The clamp 450 includes a pivoting bracket 460 that pivotsabout a pin 462 from an open configuration to a closed configuration.The clamp 450 that is illustrated in FIG. 45 pivots from the front ofthe patient to the back of the patient and is referred to as a“front-to-back” clamp. In alternative configurations, the clamp 450 maybe constructed as a “back-to-front” clamp in which the pivoting bracket460 pivots from the back of the patient to the front. The pivotingbracket 460 can be locked in the closed configuration by the fastener464 which engages and holds the pivoting bracket 460 to the L-shapedbracket 452. The fastener 464 may be a screw, bolt or the like that canbe tightened or loosened by rotation using a tool (e.g., wrench ordriver). In one embodiment, the clamp 450 further includes an optionaldetent 466 or other protuberance on the L-shaped bracket 452 that aidsin fixedly securing the clamp 450 to the rib or other anatomicalstructure.

FIG. 46 illustrates another embodiment of a clamp 470 that can be usedto secure one end of the distraction device 400 to a rib or transverseprocess. The clamp 470 includes an “J-shaped” bracket 472 that ismounted on a shaft 474. The shaft 474 terminates at a swivel joint 476that provides swiveling movement between a coupler 478 and the clampshaft 474. The coupler 478 is configured to receive one end of thedistraction rod 412 (e.g., using threads, mounting screw(s), adhesive,cement, laser weld, or the like). The clamp 470 includes a band 480secured to one end of the J-shaped bracket 472. The band 480 is flexiblein nature includes a free end 482 that is insertable into a lock 484disposed on the J-shaped bracket 472. The band 480 may be made from apolymeric material or even a metallic material. The band 480 preferablyhas a small thickness that minimizes the amount of material that isexposed to the front side of the patient. Because the patient's lungsare located somewhat near the front portion 486 of the clamp 470, it ispreferred to keep the amount of material in this section of the clamp470 to a minimum. The band 480 provides the ability to ensure that theclamp 470 is secured to the rib or other anatomical structure.

The clamp 470 that is illustrated in FIG. 46 has a band 480 that bendsabout the clamp 470 from the front of the patient to the back of thepatient and is referred to as a “front-to-back” clamp. While the clamp470 may be constructed as a “back-to-front” clamp in an alternativeembodiment, this is not preferred because of the added material thuspoints toward sensitive organs (e.g., lungs) of the patient. In oneembodiment, the clamp 470 further includes an optional detent 488 orother protuberance on the J-shaped bracket 472 that aids in fixedlysecuring the clamp 470 to the rib or other anatomical structure.

FIGS. 47 and 48 illustrate an alternative embodiment of an adjustableportion 568 that is used in connection with a distraction device 400utilizing a hollow magnet 562 (FIG. 48). While the description of theadjustable portion 568 is given in the context of the distraction device400, it should be understood that the alternative embodiment may applyequally to other distraction devices described herein (e.g., distractiondevices 140, 314, 1414, etc.). As seen in FIGS. 47 and 48, theadjustable portion 568 is contained within two slidable sections whichinclude an outer tube 548 and an inner tube 550. The outer tube 548 andinner tube 550 are moveable relative to one another as explained below.As best seen in FIG. 48, a hollow magnet 562 is mounted on an innersleeve 564 and a nut 560 having internal threads thereon. That is to saythat the inner sleeve 564 and nut 560 are entirely or at least partiallydisposed within the hollow portion of the magnet 562. The hollow magnet562, inner sleeve 564, and nut 560 rotate together in unison, betweenopposing ball bearings 556, 558. An end cap 566 holds the assemblytogether. In this embodiment, the hollow magnet 562 permits the leadscrew 554 to pass through it, thereby lessening the necessary totallength of the adjustable portion 568, and thus the length of a largerdiameter portion of the distraction device 400. Rotation of the hollowmagnet 562 effectuates rotation of the nut 560 that, depending on thedirection of rotation, either pulls inward or pushes outward the leadscrew 554 which engages with the internal threads (not shown) of the nut560. While FIG. 48 illustrates a completely hollow magnet 562, some ofthe reduced length benefits discussed above may still be gained if onlya portion of the magnet 562 were hollow or contained a recess configuredto receive the lead screw 554. The magnet 562 is advantageously apermanent magnet and may be formed from the materials described hereinwith respect to the other embodiments. Still referring to FIG. 48, adynamic seal 552 is provided at the interface between the outer tube 548and the inner tube 550 to ensure that no body fluids enter the assembly.

FIGS. 49 and 50 illustrate still another embodiment of an adjustableportion 570. This embodiment is longer but thinner as compared to theadjustable portion 468 illustrated in FIGS. 47 and 48. Again, it shouldbe understood that the alternative embodiment of the adjustable portion570 may apply to other distraction devices described herein (e.g.,distraction devices 140, 314, 1414, etc.). As seen in FIGS. 49 and 50,the adjustable portion 570 is contained within two slidable sectionswhich include an outer tube 572 and an inner tube 574. The outer tube572 and inner tube 574 are moveable relative to one another as explainedbelow. As best seen in FIG. 50, a rotatable magnet 576 is held within amagnetic cup 580 which rotates on a thrust bearing 582. The magnet 576is operatively coupled to a lead screw 578 that rotates along with themagnet 576 in response to an externally applied magnetic field asdescribed herein. The adjustable portion 570 does not include an innersheath such as that illustrated in the prior embodiment (FIGS. 47 and48) thereby enabling a thinner profile. In this embodiment, the nut 584is affixed to the inner tube 574. Rotation of the magnet 576 causesrotation of the lead screw 578 which then pulls or pushes the inner tube574 relative to the outer tube 572. A dynamic seal 586 is provided atthe interface between the outer tube 572 and the inner tube 574 toensure that no body fluids enter the assembly.

In any of the above-described embodiments, the external adjustmentdevice (e.g., external adjustment device 1130) may optionally include avibrator attached thereto that transmits vibrational motion to theadjustable portion 570 (or other adjustable portions described herein)which lessens frictional effects on the components giving them lessresistance. For example, vibration may enhance or better enable axialmotion of the outer tubes 448, 572 and inner tubes 450, 574,respectively and enhance freer rotation of the rotational components.The vibrational motion may also be delivered via a separate vibratordevice that is separate from the external adjustment device.

FIG. 51 illustrates another embodiment of a distraction system 600undergoing adjustment. In this embodiment, the implanted distractionsystem 600 includes two distraction devices 602, 604. The firstdistraction device 602 includes a first adjustable portion 606 and afirst rod 608. The first adjustable portion 606 is similar to theadjustable portion 570 of FIGS. 49 and 50, with a first cylindricalpermanent magnet 618 located at a far end of the first adjustableportion 606. The distraction system 600 includes a second distractiondevice 604 having a second adjustable portion 610 and a second rod 612.The second adjustable portion 610 is oriented in an inverted relationwith respect to first adjustment portion 606, so that a secondcylindrical permanent magnet 620 is not at the same level on the body628 (e.g., height if the subject is standing up) as the firstcylindrical permanent magnet 618. In this regard, the first and secondcylindrical permanent magnets 618, 620 are offset from one anotherrelative to their location vis-à-vis the spine. For instance, the secondcylindrical permanent magnet 620 is located higher on the body 628 whencompared to the first cylindrical permanent magnet 618.

Due to this inversion, the point of telescopic displacement 614 of thefirst distraction device 602 is also at a different level on the body628 than the point of telescopic displacement 616 of the seconddistraction device 604. Due to the oftentimes asymmetric nature of thescoliosis, it may be desired to adjust each of the distraction devices602, 604 independently from the other. As seen in FIG. 51, an externaladjustment device 622 is provided that includes a first permanent magnet624 and a second permanent magnet 626 that can be selectively placed atthe proper level (e.g., height) along the body 628 corresponding to thelocation of the permanent magnet 618, 620 of the respective distractiondevice 602, 604 intended for adjustment. The length (L) of each of thepermanent magnets 624, 626 of the external adjustment device 622 ispreferably longer than the length of the permanent magnet 618, 620 formaximal coupling, yet short enough, for example, one (1) inch long, sothat the operation of the external adjustment device 622 allows thepermanent magnets 624, 626 to sufficiently couple with the firstcylindrical permanent magnet 618, without sufficiently coupling with thesecond cylindrical permanent magnet 620. It should be noted, that in theinverted version, the second adjustable portion 610 is permanentlyattached to the second rod 612 at joint 630.

Still referring to the embodiment of FIG. 51, it may be desired toadjust the distraction length (or force) of the first distraction device602 a certain amount followed by adjustment of the distraction length(or force) of the second distraction device 604. This may beaccomplished by first placing the external adjustment device 622 overthe first adjustable portion 606 which contains the first permanentmagnet 618. The external adjustment device 622 may then be operated torotate the first permanent magnet 618 with the appropriate number ofrotations, or partial rotation as the case may be, to achieve thedesired distraction length or force. The external adjustment device 622may be operatively coupled with a PLC 1080 such as that illustrated inFIG. 14 to automatically adjust the external adjustment device 622. Forinstance, using the PLC 1080, the external adjustment device 622 may beinput to adjust the first distraction device 602 one (1.0) mm.Optionally, external adjustment device 622 and/or PLC 1080 may operateunder feedback control. For instance, the acoustic feedback modalitydescribed with respect to FIGS. 15-30 may be used to listen for anacoustic signal (e.g., clicks). As another alternative, an opticalfeedback, force feedback, or magnetic Hall effect feedback control maybe used to provide feedback control of the external adjustment device622.

Once the first adjustable portion 606 has been adjusted as desired, theexternal adjustment device 622 is moved over the second adjustableportion 610 which contains the second permanent magnet 620, for exampledirectly over the permanent magnet 620. The external adjustment device622 may then be operated to rotate the second permanent magnet 620 withthe appropriate number of rotations, or partial rotation as the case maybe, to achieve the desired distraction length or force. For instance,the external adjustment device 622 may be input to adjust the seconddistraction device 604 one-half (0.5) mm. This may be conducted asdescribed above with respect to the first distraction device 604,including the option use of the PLC 1080 with feedback control.

While the independent adjustment described above pertains to applicationof a particular distraction distance (e.g., 1 mm or 0.5 mm), it shouldalso be understood that the external adjustment device 622 may be usedto adjust the first distraction device 602 to a different distractionforce than the second distraction device 604. For instance, the firstdistraction device 602 may be adjusted to have a force of 40 pounds,while the second distraction device 604 may be adjusted to 30 pounds. Ofcourse, one alternative is leave on the distraction devices 602, 604 atits current or then-current setting with adjustment only being performedon the other distraction device 602, 604.

In still another embodiment, a magnetic shield 632 is used that permitsthe first and second cylindrical permanent magnets 618, 620 to be closerto one another. For example, if it is desired to adjust the firstdistraction device 602 and not the second distraction device 604, themagnetic shield 632 is placed at location 634. The external adjustmentdevice 622 is placed with its permanent magnets 624, 626 in proximity tothe first cylindrical permanent magnet 618. The magnetic shield 632diminishes the ability for the permanent magnets 624, 626 to be able tomagnetically couple with the second cylindrical permanent magnet 620.The magnetic shield 626 may then be placed at a different location,closer to the first cylindrical permanent magnet 618, in order toindependently adjust the second cylindrical permanent magnet 620. Themagnetic shield 632 may be made from nickel, iron, steel or anickel-iron alloy such as Mu-Metal, for example 75% Nickel/15% iron.Other materials with similar magnetic shielding properties may also beused.

FIG. 52 illustrates another embodiment of a technique for the emergencyadjustment of a distraction device 638. As seen in FIG. 52, the patient636 has an implanted distraction device 638 similar to those describedherein. In some instances, the patient 636 may be in need of emergencyadjustment due to any number of reasons including, for example,incorrect prior adjustment, trauma, bone, joint muscle or connectivetissue pain, pregnancy, or growth.

If the patient 636 arrives at a hospital that does not have the externaladjustment device 1130, 622 available for use, the implanted distractiondevice 638 containing the cylindrical permanent magnet 640 may beadjusted by using a magnetic resonance imaging (MRI) scanner 642—adiagnostic instrument that is commonly found in hospitals. Magneticresonance imaging (MRI) scanners 642 contain a primary magnet 644comprising a supercooled electromagnetic coil. The primary magnet 644 isdesigned to be “always on”, except in cases of maintenance ormalfunction. The primary magnet 644 generates a very large magneticfield (i.e., magnetic flux density). Older MRI scanners had magneticfields of 0.2 Tesla, for example, but most today have fields of 1.5Tesla or 3 Tesla while still others are 7 Tesla.

Generally, all of these fields will strongly orient a cylindricalpermanent magnet 640, 394 so that it is aligned with the magnetic fieldof the primary magnet 644 if it is near the MRI scanner 642. It shouldbe understood that while a description is given with respect to drivenmagnet 640, the acoustic sensing features may also apply to magneticelement 218 of FIGS. 6C-6G, the internal magnet 1064 of FIGS. 13A-13D,14, the internally located driven magnet 1402 of FIG. 35, cylindricalmagnet 394 of FIGS. 41, 42, and 44, the hollow magnet 564 of FIG. 48,magnet 576 of FIG. 50, magnet 262 of FIG. 53, magnets 618, 620 of FIG.51, and magnet 1302 of FIGS. 15-30.

The torque required to turn the cylindrical permanent magnet 640 into adifferent orientation than the MRI aligned orientation would besignificantly high, and much greater than the rotational resistance ofthe cylindrical magnet assembly. Therefore, by placing a patient 636close to the primary magnet 644 of the MRI scanner 642 (for example, ata distance of ten feet or less, or more specifically five feet or less)and by turning the body of the patient in either a first rotationaldirection 646 or a second rotational direction 648, the implanteddistraction device 638 may be adjusted without the need of an externaladjustment device 1130, 622. Generally, the patient turns or rotates himor herself about an axis of rotation (which may change slightly duringthe rotational procedure). For example, the patient may stand on theirfeet and turn their body. Alternatively, the patient may sit in a swivelchair, for example a chair made of MRI safe materials such as aluminum,and the chair may be spun in the desired direction. If patient turns oris turned in first rotational direction 646, the distraction is reduced.If patient turns or is turned in second rotational direction 648, thedistraction is increased. It is desirable that the implanted distractiondevice 638 is well secured to the patient 636, for example with pediclescrews, hooks or clamps, so that the attraction of the cylindricalpermanent magnet 640 to the primary magnet 644 of the MRI device doesnot cause unsafe displacement of the implanted distraction device 638 atits fixation points. Additionally it is preferable to use mostlynon-magnetic materials in the implant, such as Titanium or Titaniumalloys such as Ti-6AL-4V, so that the implant itself is not stronglyattracted to the primary magnet 644. If the implanted distraction device638 uses acoustic feedback, such as that described in FIGS. 15 through34, medical personnel may listen to the patient with an MRI safestethoscope to confirm that clicks are heard, which would indicate thatthe magnet 640 is indeed turning. The clicks may also be counted inorder to quantify the amount of adjustment precisely.

The above-described use of the primary magnet 644 to adjust the magnet640 of the distraction device 638 may also be employed in otherimplantable devices that utilize a rotating or cyclically-movablemagnet. For instance, the implantable device may include a restrictiondevice (e.g., gastric band or annuloplasty ring), or a valve, or theother devices. Examples of such devices that may be adjusted in thismanner may be found in U.S. Patent Application Publication Nos.2008-0097487 and 2008-0097496. For this method to work, it should benoted that the magnets don't have to be cylindrical, but the axis ofmagnetization should not be parallel to the axis of rotation.

As mentioned, one of the benefits of a fully fusionless procedure is theability to remove the implants after the spine has been able to bemanipulated by the initial surgery and the non-invasive adjustments ofthe distraction device. The embodiments described herein allow for acompletely adjustable scoliosis treatment system, which can achieve thegoal of a straightened spine and no lifetime implant through a total oftwo surgical procedures; one procedure to implant the device and oneprocedure to remove the device. This is a significant improvement to theadjustable scoliosis treatment devices which have been proposed, andrequire adjustment techniques utilizing surgical incisions. It should benoted that after the initial implant procedure, the physician may desireto have the patient use a brace for a one or a few months, in order toprotect the healing process. This protective brace serves a differentpurpose than the scoliosis braces that attempt to affect the patient'sCobb angle.

It is envisioned that patients may be identified for their geneticsusceptibility to scoliosis and treated with a distraction device asdescribed herein. For example, a genetic test may identify that aparticular subject that has a current Cobb angle of less than or equalto 30° is predisposed or otherwise at risk for his or her Cobb angle toincrease beyond this initial angle (e.g., increase to or beyond 40°). Inthis regard, a genetic test may be run on the patient's nucleic acid(e.g., DNA or RNA) to identify genes or gene sequences that areassociated with this predisposition. If the patient has this geneticsusceptibility, a distraction device of the type described herein may beused to preemptively correct or mitigate the anticipated spinalmalformation. For example, Gao et al. have been reported that CHD7 genepolymorphisms are associated with susceptibility to idiopathicscoliosis. Gao et al., CHD7 Gene Polymorphisms Are Associated withSusceptibility to Idiopathic Scoliosis, American Journal of HumanGenetics. Vol. 80, pp. 957-65 (May, 2007). The above-noted Gao et al.publication is incorporated herein as if set forth fully herein. Inparticular, the CHD7 gene spans 188 kb and contains one non-coding exonand thirty-seven coding exons. The SNP loci associated with idiopathicscoliosis were contained within an ˜116 kb region encompassing exons 2-4of the CHD7 gene. For example, the genetic test may look for the SNPloci discussed above which are associated with IS susceptibility.

Though many of the embodiments described herein have generally been inthe area of adolescent idiopathic scoliosis and early onset scoliosistreatment, it is contemplated that the devices and methods describedherein also have application in the treatment of adult scoliosis. Adultscoliosis can continue to worsen with time. Though the adult isskeletally mature, the Cobb angle may still continue to increase withtime. The relaxation or slight reduction in height that occurs in adultsmay have some relation with this increase in Cobb angle. Curves above1000 are rare, but they can be life-threatening if the spine twists thebody to the point where pressure is put on the heart and lungs. Thedevices and methods described herein can also be used to treat adultscoliosis, e.g., allowing adult scoliosis to be treated with a minimallyinvasive and/or fusionless approach. In addition, gradual adjustment ofthe spine may be desired, especially in the cases of very high Cobbangles. For example, it may be desired to limit the amount of stresseson the bones or on the implant materials, by first adjusting an adultscoliosis patient so that their Cobb angle is reduced 50% or less, then15% or less each few months, until the spine is straight. As oneexample, the initial surgical implantation may reduce the Cobb angle by50% or more by the physician performing manual distraction on the spine.Post-implantation, the Cobb angle can be reduced in a non-invasivemanner by application of a constant or periodically changing distractionforce. A first non-invasive adjustment may result in a Cobb anglereduction of less than 50%. Additional non-invasive adjustments may beperformed which result in even smaller Cobb angle reductions (e.g., lessthan 15% from original Cobb angle).

In this regard, the Cobb angle may be reduced by a smaller amount overthe next few months (e.g., less than around 15% each monthpost-operation). The non-invasive adjustment of a fusionless implantmade possible by the invention allows for a gradual adjustment scheme ofthis nature. Moreover, the distraction forces used over this period oftime are generally low (e.g., distraction force less than 45 pounds)which means, among other things, less patient discomfort, and lesschance of failure within the adjustable rods 142, 144. Non-invasiveadjustments may be periodically performed when the patient visits his orher physician. This may occur over a span of more than one week (e.g., aseveral week process). Of course, the number and periodicity of theadjustments is a function of, among other things, the Cobb angle of thepatient.

Oftentimes, the adult spine has less dense or even osteoporotic bone, soit may be desirable to combine the sort of gradual adjustment describedhere with additional methods to strengthen the bone, for example thebone of the vertebral bodies. One method is to strengthen the vertebralbody by performing prophylactic vertebroplasty or kyphoplasty, whereinthe internal area of the vertebral body is strengthened, for example byinjection of bone cement or Polymethyl Methacrylate (PMMA).Additionally, if pedicle screws are used for fixation, the surface ofthe screws may be treated with a biologic material that promotes bonegrowth, or a surface characteristic that improves bone adhesion. Any ofthese methods would further improve the possibilities that thedistraction forces would not cause fracture or other damage to thevertebrae of the patient.

Another embodiment includes a bone growing implant, wherein themanipulation of a portion of the skeletal system is limited to a singlebone, and the bone growing implant is a distraction device, capable ofdistracting a first and second locations located on or in the same bone.For example, in many cases of dwarfism, the femur and the humerus bonesare short in relation to the other bones. Currently these bones may begrown longer using a device such as the Taylor Spatial Frame, which isan external frame having wires or pins that extend through the skin andattach to the bone. The frame can be continually adjusted by theexternal adjustment knobs to stimulate bone growth in the desireddirection. This device may also be used on patients whose bones stopgrowing due to, for example, pediatric bone cancer, such as Ewing'ssarcoma or osteosarcoma. Another application for this device is inpatients who have had broken bones which are healing in anunsatisfactory manner, for example, in the case of one leg that isshorter than the other because of a badly healed femur fracture. Oneproblem that is seen with the Taylor Spatial Frame is the occurrence ofpin tract infections, which occur because there is an open channel forbacteria to enter from the outside of the patient to the bone. Anotherapplication for bone growth is for selective growth to only one side ofthe bone, for example in Blount's disease (bowleggedness), in which oneside of the bone grows normally while in the other side there is anarrest in the growth plate.

In all of these bone growth applications, a non-invasively adjustablebone growth distraction device is needed. A device of this nature ispresented as an embodiment of this invention in FIG. 53. A bone growthdistraction device 272 is attached to bone 256 having a proximal portion258 and a distal portion 260 by a proximal securement member 276 and adistal securement member 278. The securement members 276, 278 mayoperate using any number of securement devices or methods known toattach a device to bone, including screws, clamps or even adhesivematerials. In cases of a bone fracture, a fracture site 274 isillustrated, though it should be noted that this fracture is not alwayspresent in some of the applications previously mentioned. As seen inFIG. 53, the bone growth distraction device 272 includes a cylindricalmagnet 262 that is configured to rotate on its axis in response to anexternally applied magnetic field (as described above in the context ofother embodiments). Rotation of the cylindrical magnet 262 effectuatesrotation of a planetary gear set 266. An optional slip clutch 264 isillustrated as being disposed between the cylindrical magnet 262 and theplanetary gear set 266, though slip clutch 264 may be disposed at anyother location along the drive transmission. Rotation of the planetarygear set 266 in a first direction (e.g., either clockwise orcounter-clockwise depending on configuration) causes lead screw 268 toturn within internal thread 270 causing distraction (e.g., elongation)of the bone 256. Bone growth distraction device 272 may be implanted ina single operation. Subsequent adjustments are performed non-invasively,and if desired can be performed frequently in order to precisely controlbone growth. An adjustment device such as external adjustment device1130 described herein may be used to rotate the cylindrical magnet 262.The cylindrical magnet 263 may be dimensioned and made of the samematerials as described herein with respect to the other embodiments.

While FIG. 53 may be especially effective in treating Blount's disease,or any other condition that requires selective growth (for example onone side of the bone). FIG. 54 illustrates an alternative embodiment ofthe invention incorporating an intramedullary magnetic elongationdevice. Bone distraction device 271 is placed within the intramedullarycanal 273 and secured at first attachment point 275 and secondattachment point 277. By being centered within the intramedullary canal273, the bone distraction device 271 is capable of lengthening the bone256 substantially parallel to its longitudinal axis 279. It should beunderstood that the embodiments described herein may be applicable tobones and/or skeletal structures other than those specifically describedor illustrated in the drawings. For instance, the embodiments may beutilized in the tibia, mandible, jawbone, and the like.

Other orthopedic distraction devices are conceived using the presentinvention. FIG. 55 illustrates a distraction device 1101 configured forreplacement of an intervertebral disk, and for distraction between afirst vertebral body 1103 and a second vertebral body 1105.Intervertebral disks can degenerate, bulge, herniate or thin, and causeaccompanying back pain. Degenerative disk disease (DDD) has caused alarge increase in the use of intervertebral disk replacement devices.Current intervertebral disk replacement devices have had incompletesuccess, due to a large rate of patients whose pain returns with time.The inventive art describes an intervertebral disk replacement devicethat allows for additional adjustment after disk replacement surgery andafter the healing period. If a patient has recurring pain, the devicemay be adjusted non-invasively to increase or decrease distraction inorder to eliminate recurrent pain. Using the external adjustment device1130 in the same non-invasive manner as the other embodiments aninternal magnet 1107 is non-rotated. Internal magnet 1107 is coupled tolead screw 1109 so that rotation motion changes the displacement betweenlead screw 1109 and the female thread 1111 inside a portion of thedistraction device 1101.

This technique may also be used to treat other spinal problems, such asspondylolisthesis. In certain situations, the entire vertebral body maybe removed, for example due to a crushed, fractured or diseasedvertebral body. The embodiment of FIG. 55 may be supplied in a number ofsizes, for example thicknesses, in order to fill the desired dimensionbetween the other vertebral bodies.

FIGS. 56 through 60 illustrate a device for modification of a fracturedvertebra is illustrated. Vertebrae can become weak with osteoporosis,and may fracture easily, causing an increased kyphosis and increasingthe risk of fracture of subsequent vertebrae. Fractured vertebral body800 is illustrated in FIG. 56. The fracture shown is a wedge fracture,which is very common in this type of patient. Anterior height H has beensignificantly reduced in comparison to original height h. Currently,fractured vertebrae can be treated by a vertebroplasty procedure, inwhich cement, for example polymethyl methacrylate (PMMA) is injectedinto the inside of the vertebral body. Vertebroplasty does very littlein terms or restoring height. An alternative method known as kyphoplastyis sometimes performed during which a balloon is inflated inside thevertebral body to crush in inner bone material prior to filling with thecement. Kyphoplasty has shown to increase height slightly, but theheight gain is still considered unsatisfactory by many surgeons. In analternative embodiment of the invention illustrated in FIG. 57 a hole isdrilled through one of the pedicles 802 which lead to the vertebral body800. Cannula 804 is placed through the hole and distraction device 806is placed through the cannula 804. If desired, a kyphoplasty balloon maybe placed through the cannula first in order to pre-dilate. Cannula 804may be partially or completely removed at this point. Distraction device806 comprises a protective sheath 812, a distraction head 808 and acylindrical magnet 810. Protective sheath 812 is configured to besecured inside of pedicle 802 and/or inside vertebral body 800.Cylindrical magnet 810 is free to rotate within protective sheath 812and is coupled to externally threaded shaft 814. As cylindrical magnet810 is rotated by an external rotating magnetic field (for example thatfrom external adjustment device 1130) threaded shaft 814 rotates withininternal thread 816 causing threaded shaft 814 to extend axially. Asthreaded shaft 814 extends, dilating tip 818 is forced throughseparation 820, forcing apart first distractor 822 and second distractor824 and increasing the height of the fractured vertebral body from H₁ toH₂. It can be appreciated that the external adjustment device 1130 canapply a significant torque to the cylindrical magnet 810 and thus allowa high separation force applied to the two distractors 822, 824 of thedistraction head 808. Several options are now possible at this point.

In the first option, the cylindrical magnet 810 may be removed from theassembly and cement may be applied through the protective sheath 812 tofully set the vertebral body in its distracted configuration, leavingthe protective sheath 812 and the distraction head 808 permanentlyimplanted.

In the second option, no cement is applied and the patient is recoveredwith the entire distraction device 806 intact. After reviving fromanesthesia, and most likely also following recovery from the normal painthat accompanies post-surgery, the patient returns for a non-invasiveadjustment, wherein the distraction device is adjusted to the specificdistraction height that most reduces pain. For example. FIG. 60 showsthe dilating tip 818 having a tapered outer diameter 826. By adjustingthe distraction device 806 in either direction, the extent of the spreadof the two distractors 822, 824 can be controlled. Though thedistraction head 808 may be made from numerous metallic or polymericmaterials, it may be preferably made of a highly elastic metal, such asnickel-titanium, so that the two distractors 822, 824 will returntowards their original unexpanded configuration as the dilating tip 818moves in direction A. This entire non-invasive adjustment process hasnot been possible with prior devices which could only be manipulatedduring surgery, when patient is unconscious. Once the patient is at adesired adjustment level with little or no pain, an additional proceduremay be performed to remove the magnet and/or inject cement.

In the third option, the cement is injected at the end of the initialimplantation operation, but the distraction device 806 is left intact.It is common for cement to remodel or even recede, for example after 18months. With the present invention, this is less likely, because thedistraction head 808 in its expanded configuration serves as additionalreinforcement. In addition, if the cement were to remodel or recede, anadditional adjustment procedure can be performed during which the twodistractors 822, 824 are further spread and more cement is injected.

FIG. 61 illustrates the present invention incorporated into a motionpreservation (or dynamic stabilization) device 828. The motionpreservation device 828 is attached to a first vertebra 830 and a secondvertebra 832 with pedicle screws. First and second vertebrae 830, 832are separated by intervertebral disk 834. Second head 838 is static andis attached to second vertebra 832. First head 836 is adjustable andcomprises first portion 842, which is attached to first vertebra 830 andsecond portion 844 which is can be adjusted by using external adjustmentdevice 1130 to rotate internal magnet 846. Intermediate portion 840comprises an outer spacer 848 and an inner cord 850. Outer spacer 848and inner cord 850 are preferably made from polymeric materials thatallow for some deformation and therefore limited movement between firstvertebra 830 and second vertebra 832. By non-invasively adjusting firsthead 836 with the external adjustment device 1130, the length L can bemanipulated so that the desired condition is reached wherein the rangeof motion allowed by the implant is tailored so that it is within therange of motion where no pain is encountered, and the range of motionfor which pain is present is eliminated. Current dynamic stabilizationdevices do not have this non-invasive adjustability. Therefore, asurgeon is never sure whether the patient's device will maintain a rangeof motion for which patient feels no pain. The embodiment of thisinvention allows the ability to adjust the device while the patient isnot under anesthesia and after the patient has recovered from anypost-surgery pain, so that the real pain that is intended to be curedcan actually be assessed.

While embodiments of the present invention have been shown anddescribed, various modifications may be made without departing from thescope of the present invention. The invention, therefore, should not belimited, except to the following claims, and their equivalents.

What is claimed is:
 1. A distraction device comprising: a distractionrod having a first end and a second end; and an adjustable portioncoupled to the second end of the distraction rod, the adjustable portioncomprising: a sleeve having a bore extending longitudinally through atleast a portion of a length of the sleeve; a lead screw disposed withinthe bore; an offset gearing assembly configured to rotatably drive thelead screw into or out of the bore; and a cover disposed over theadjustable portion.
 2. The distraction device of claim 1, wherein theoffset gearing assembly comprises: a drive member configured to rotateabout an axis of rotation in a first direction, wherein the firstdirection is one of clockwise or counter clockwise; a first toothed gearcoupled to the drive member, wherein the first toothed gear isconfigured to be rotated by the drive member in the first direction; anda second toothed gear coupled to the lead screw, wherein the firsttoothed gear is configured to cause rotation of the second toothed gearand the lead screw in the first direction.
 3. The distraction device ofclaim 2, wherein the drive member comprises a cylindrical magnet havinga first end and a second end, wherein the cylindrical magnet isconfigured to be rotated by an external adjustment device.
 4. Thedistraction device of claim 2, wherein the cylindrical magnet isrotationally held by a first cup at the first end and a second cup atthe second end, and the cylindrical magnet is configured to rotatebetween a first ball bearing at the first end, and a second ball bearingat the second end.
 5. The distraction device of claim 2, wherein theoffset gearing assembly further comprises: a third toothed gearconfigured to mesh with the first toothed gear, the third gear beingconfigured to rotate in a second direction, in response to rotation bythe first toothed gear in the first direction, wherein the seconddirection is the other of clockwise or counter clockwise, and isopposite the first direction; and a fourth toothed gear secured to andconfigured to rotate with the third toothed gear, and to mesh with thesecond toothed gear, wherein the second toothed gear is configured torotate in the first direction, in response to rotation by the third andfourth toothed gears in the second direction.
 6. The distraction deviceof claim 2, wherein the first toothed gear has eight (8) teeth, and thesecond toothed gear has eighteen (18) teeth.
 7. The distraction deviceof claim 5, wherein the third toothed gear has eighteen (18) teeth, andthe fourth toothed gear has ten (10) teeth.
 8. The distraction device ofclaim 5, wherein the first toothed gear meshes with the third toothedgear at a gear ratio of 18:8.
 9. The distraction device of claim 5,wherein the fourth toothed gear meshes with the second toothed gear at agear ratio of 18:10.
 10. The distraction device of claim 2, furthercomprising a thrust bearing disposed in a face-to-face arrangement withthe second toothed gear, the thrust bearing being configured to reducefrictional forces during rotation of the lead screw.
 11. The distractiondevice of claim 1, wherein the first end of the distraction rod isconfigured to be cut to achieve a desired length to fit a subject'sanatomy.
 12. The distraction device of claim 1, wherein the distractionrod is configured to be bendable into a custom configuration to fit asubject's anatomy.
 13. The distraction device of claim 1, furthercomprising: an annular dynamic seal disposed between the distraction rodand the cover, the annular dynamic seal being configured to permit thedistraction rod to pass through an end of the adjustable portion withoutallowing a body fluid to enter the adjustable portion.
 14. Thedistraction device of claim 1, further comprising: a first anchorconfigured to affix the first end of the distraction rod to a first boneportion in a subject; and a second anchor configured to affix theadjustable portion to a second bone portion in the subject, wherein thefirst anchor and the second anchor are each independently selected froma hook, a clamp, and a screw system.
 15. The distraction device of claim1, wherein the offset gearing assembly comprises a gear ratio of 81:10.16. The distraction device of claim 1, wherein the offset gearingassembly is configured to provide an output to input torque ratio of4.05.
 17. The distraction device of claim 1, wherein the bore isthreaded.
 18. The distraction device of claim 2, wherein rotation of thedrive member in the first direction causes the offset gearing assemblyto rotatably drive the lead screw into the bore, and rotation of thedrive member in the second direction causes the offset gearing assemblyto rotatably retract the lead screw out of the bore.
 19. The distractiondevice of claim 18, wherein the rotation of the drive member in thefirst direction is configured to provide an increased distraction force,and wherein the rotation of the drive member in the second direction isconfigured to provide a decreased distraction force.
 20. The distractiondevice of claim 3, wherein the cylindrical magnet comprises one or moreof Neodymium-Iron-Boron, Samarium Cobalt, Aluminum Nickel Cobalt, IronPlatinum, or Vanadium Permendur.